Plasma-Enhanced ALD of HfOx for Effective Surface Passivation of Silicon: A Material and Interface Study

Plasma-Enhanced ALD of HfOx for Effective Surface Passivation of Silicon: A Material and Interface Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Plasma-Enhanced ALD of HfO x for Effective Surface Passivation of Silicon: A Material and Interface Study Rinki ., Meenakshi ., Paras ., Anil ., Shivanshu ., Uttam Kumar Goutam, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8590256/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study investigates the silicon surface passivation characteristics of hafnium oxide (HfOₓ) thin films deposited using plasma-enhanced atomic layer deposition (PEALD), with a particular focus on remote plasma power ( P w ) induced growth mechanism of the films. The HfOₓ films were grown on Si (100) wafers at a substrate temperature of 200°C using tetrakis(ethyl-methyl-amino)hafnium (TEMAHf) as the metal precursor and oxygen plasma as the oxidant. Structural analysis performed using grazing incidence X-ray diffraction (GIXRD) confirmed the amorphous nature of all the films, while atomic force microscopy (AFM) revealed smooth surfaces with roughness < 0.2 nm. The variation of films thickness, as evaluated using, spectroscopic ellipsometry showed that growth per cycle (GPC) varied with plasma power. XPS analysis revealed that plasma power of 2500 W effectively suppressed oxygen-related defect states in the HfOₓ films. A maximum effective minority carrier lifetime ( τ eff ) of 390 µs, corresponding to a surface recombination velocity (SRV) < 50 cm/s was achieved for the films with a thickness of 16 nm, deposited at a P w of 2500 W. Plasma induced modifications on silicon surface were studied using electrical characterization of its MOS capacitors and the results indicate that chemical passivation at the Si/HfOₓ interface played a dominant role in reducing the interface trap density ( D it ). These results emphasise the critical role of plasma power in optimizing the growth dynamics and passivation performance of PEALD-grown HfOₓ films for advanced silicon-based devices. Surface passivation PEALD HfOₓ Impedance spectroscopy Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction One of the effective strategies to lower solar cell fabrication costs is to lower the thickness of crystalline silicon (c-Si) substrates, thereby minimizing material usage. However, thinner wafers are more susceptible to charge carrier recombination at the surfaces, which degrades the device performance. Consequently, effective suppression of surface recombination is essential for maintaining high efficiency and ensuring cost-effective production of industrial silicon photovoltaics [ 1 ]. The process of minimizing charge carrier recombination at the crystalline silicon (c-Si) surface is known as “surface passivation”. This is typically achieved using a dielectric thin film that mitigates recombination losses either by chemically terminating dangling bonds, thereby reducing the D it (chemical passivation) or/and by using built-in fixed charges that repel one type of charge carrier (electron or hole) away from the surface, referred to as field effect passivation [ 1 – 4 ]. A wide range of dielectric materials has been explored in recent past to mitigate defect-assisted Shockley-Read Hall (SRH) recombination, including Al-doped ZnO [ 5 ], TiO 2 [ 6 , 7 ], ZrO 2 [ 8 ], SiO x [ 9 ], SiN x [ 10 ], a-Si:H [ 11 ], ZnO, Al 2 O 3 [ 12 , 13 ], and HfO x [ 1 , 14 ]. Amongst these materials, hafnium oxide (HfO x ) is of particular interest, especially in microelectronics, due to its exceptional electrical and optical properties, including a high dielectric constant (k = 16–25), a wide bandgap (5.6–5.8 eV), a refractive index of approximately 2-2.1 and excellent thermal and chemical stability with silicon. Its optical transmittance in the visible range makes HfO x a promising material for use in high-k gate dielectrics, surface passivation layers and antireflection coatings (ARCs) [ 1 , 15 , 16 ]. However, the deposition method HfO x plays a key role in determining the effectiveness of passivation quality of the resulting layers. ALD has gained considerable attention for depositing conformal and ultrathin dielectric films with precise thickness control [ 17 ]. PEALD offers advantages over thermal ALD, including enhanced film quality at lower deposition temperatures [ 18 , 19 ], which arises from the high reactivity of plasma-generated species. In addition, PEALD enables access to a broader processing parameter window such as increased growth rates per cycle, better control over stoichiometry and composition, compatibility with a wide range of precursors, and superior film characteristics at lower processing temperatures that are often unattainable using thermally driven ALD processes. These features make PEALD a promising method for the deposition of high-quality HfO x films with improved electrical and interface properties on silicon substrates. Despite its potential, the application of PEALD-deposited HfO x for silicon surface passivation remains relatively underexplored. Only a few studies have evaluated its effectiveness in enhancing minority carrier lifetime. Meenakshi et al. [ 20 ] reported SRV of approximately 10 cm/s for HfOₓ films with a thickness of ~ 23 nm deposited on p-type silicon substrates. Rajbir et al. [ 14 ] achieved SRV below 40 cm/s using PEALD-grown HfO x on n-type silicon. Zhang et al. investigated the influence of oxygen plasma pre-treatment followed by subsequent annealing reporting an improved minority carrier lifetime of 67 µs [ 21 ]. Ailish et al. showed that a 12 nm thick HfO x layer on n-Si could yield an SRV as low as 4.1 cm/s [ 22 ]. Given these promising yet limited findings, this work systematically investigates the passivation mechanisms of PEALD-deposited HfO x on n-type substrates, with an emphasis on optimizing the P w for achieving high quality minority carrier lifetime at lower film thickness. The effectiveness of surface passivation has been evaluated through minority carrier lifetime measurements and explored the underlying HfO x passivation mechanism as a function of P w , which modulates D it at the interface of HfO x /Si. The interface characteristics have been analysed using capacitance and conductance measurements. The results were analysed in detail to provide insights into optimizing HfO x based dielectric layers for silicon photovoltaics. 2. Experimental 2.1. Sample preparation Surface passivation was examined using moderately doped float-zone n-Si substrates (, 0.5-4 Ω-cm, 350 ± 25 µm). All samples underwent standard RCA cleaning procedures (SC-I and SC-II) before being introduced into reaction chamber. PEALD of HfO x was carried out using (M/s Picosun, Model R200) reactor equipped with a remote plasma source (M/s Advanced Energy). The films were deposited using tetrakisethyl-methyl-amino)hafnium [TEMAHf, Hf(N(C₂H₅)(CH₃))₄] as the hafnium precursor and oxygen plasma as oxidizing agent. Each ALD cycle included two half-cycles: one for TEMAHf exposure and one for O₂ plasma exposure, separated by nitrogen purging steps to eliminate unreacted precursors and byproducts. To maintain efficient precursor delivery, TEMAHf source was maintained at 120°C to compensate for its low vapor pressure, while delivery lines were maintained at 150°C to prevent condensation. The films were deposited at varying P w in the range of 2000 W − 2500 W. All the samples were subjected to rapid thermal annealing (Model: AS-one 150, M/s Annealsys, France) at 400°C for 12 minutes under nitrogen ambient to enhance surface passivation. For electrical measurements, metal-oxide-semiconductor (MOS) structures were fabricated by thermally evaporating aluminium contacts (1 mm diameter) onto the HfO x surface, while rear surface was fully coated with aluminum. 2.2. Measurement techniques Film thickness was measured using a spectroscopic ellipsometer (VASE, model: M2000, M/s J.A. Wollam Company. Inc., USA). Structural analysis was carried out using GIXRD (Model: PAN analytical Xpert PRO MRD), operated in grazing incidence mode at a fixed incidence angle of 1°. Interfacial layer formation and bonding characteristics were investigated using fourier transform infrared spectroscopy (FTIR) (Model 2000, M/s Perkin Elmer spectrometer, USA). Surface morphology of the HfOx films was studied using atomic force microscope (AFM, Multimode V, Veeco Instruments) measurements. X-ray photoelectron spectroscopy (XPS) measurements were performed at the hard X-ray photoelectron spectroscopy (HAXPES) beamline BL-14 of the indus-2 synchrotron facility, Indore, India. The beamline is equipped with a Si (111) double crystal monochromator (DCM) and a PHOIBOS 225 electron energy analyzer (Specs). The measurements were conducted using incident X-ray photons with an energy of 4065 eV. The τ eff was measured with the sinton lifetime tester based on photoconductance decay (Model: WCT-120). Electrical measurements were carried out on MOS structures using gamry instruments (Gamry Reference 600 Potentiostat/Galvanostat/ZRA, Inc., USA). A 10 mV AC voltage signal was applied along with DC bias to meet small-signal requirements for accurate measurements of oxide capacitance. 3. Results and discussion 3.1. Film thickness The HfOₓ film thickness and refractive index were extracted from ellipsometry measurements performed at three incident angles (65°, 70°, and 75°), over a wavelength range of 245–1700 nm. The thickness of HfO x was found to depend on the applied P w . As shown in Fig. 1 (a), the extracted thickness exhibits a non-linear relationship between the film thickness and P w , where thickness initially decreases as P w increases from 2000 W to 2200 W, and then increases at higher power. This behaviour suggests a transition in growth mechanism, which could be due to competing surface reactions at higher plasma energies [ 23 ]. The refractive index spectra, shown in Fig. 1 (b) exhibit normal dispersion behaviour across wavelength range of 245–1700 nm with minimal variation for the films deposited at different P w . This indicates that the optical properties remain consistent despite variations in deposition conditions. The films exhibited a refractive index of approximately 2 at a wavelength of 632.8 nm, with a variation in band gap from 5.3 eV to 5.6 eV in studied P w range. The results are in good agreement with earlier studies reported on ALD-grown HfO₂ thin films [ 20 ]. 3.2. Film crystallinity and composition The structural properties of HfO x thin films were investigated using GIXRD. Figure 2 (a) shows the GIXRD spectra of the films deposited at different P w . The absence of distinct diffraction peaks related to HfO x indicates that the deposited films are amorphous. However, a prominent peak observed at 52°, accompanied by a hump at 54°, is associated with the silicon substrate beneath the film [ 20 ]. As can be seen from Fig. 1 (a), higher power (2500 W) during the deposition enhances the growth rate and density of the HfO x film, leading to a better coverage of the silicon substrate. This improved coverage further reduces the penetration of X-rays to the silicon substrate, reducing the silicon substrate peak intensity at 2500 W power. HfO x is known to exhibit multiple crystalline phases, such as monoclinic, orthorhombic, and tetragonal phases. In general, the crystallinity of thin film is influenced by several parameters, including deposition method, substrate temperature and post-deposition annealing (PDA) conditions. PEALD is a low-temperature process often results in amorphous films. However, after upon PDA, crystalline phases could emerge depending on the annealing conditions. 3.2.1. FTIR analysis Figure 2 (b) shows the FTIR spectra of HfO x films deposited at various P w . The peak observed in the wavenumber range, 550–650 cm − 1 is associated with Hf-O vibrational modes. Additionally, signal near 610 cm⁻¹ arises from Si-Si vibrational mode from the substrate [ 24 ]. The peak at 738 cm − 1 corresponds to the monoclinic phase of HfO x , while the broad absorption around 890 cm − 1 is associated with Si-H bonds. Peaks observed in the 1000–1200 cm − 1 range and at 816 cm − 1 correspond to Si-O stretching vibrations, indicating that oxygen from the plasma or the Hf precursor reacted with the silicon substrate during deposition, forming a thin interfacial SiO 2 ​ layer. The peak observed at 967 cm − 1 is associated with the formation of a thin Hf-Si-O interfacial layer (IL), which could be developed during hafnium oxide deposition. Similar observations were reported for HfO 2 films deposited by UV-photo-CVD [ 25 ]. The FTIR analysis further indicates that there are no distinct changes in the functional groups of the layers or at the interface with varying P w . 3.2.2. X-ray photoelectron spectroscopy X-ray photoelectron spectroscopy (XPS) was performed to investigate the chemical bonding states of the HfO x thin films. The binding energy scale was calibrated using the C 1s peak positioned at 284.8 eV as an internal reference. Figure 3 (a) shows the Hf 4d core-level spectra for the films deposited at P w of 2000 W and 2500 W. Two distinct peaks are observed at the binding energies of 213.3 ± 0.4 eV and 223.6 ± 0.3 eV corresponding to Hf 4d₅/₂ and Hf 4d₃/₂, respectively. Figure 3 (b) shows the O 1s core-level spectrum, which is deconvoluted into two peaks, O I at 529.5 ± 0.3 eV corresponds to Hf-O bonds in HfO x , while O II around 532.5 ± 0.1 eV is attributed to surface hydroxyl (-OH) groups or oxygen-related defects [ 26 , 33 ]. Although no significant shift in the binding energies of these peaks is observed with increasing deposition power, a noticeable reduction in the O II (532.5 eV) peak area (Table 1 ) at 2500 W indicates a decrease in defect-related oxygen species. This reduction correlates with the improved passivation behavior observed in the C-V measurements, suggesting that oxygen-deficient and hydroxyl-related defects are effectively suppressed at higher deposition power. The XPS spectral parameters corresponding to the O 1s and Hf 4d core levels are summarized in Table 1 . Table 1 XPS peak fit parameters corresponding to Hf 4d and O 1s. Power (W) 2000 2500 Peak position(eV) FWHM (eV) Area Peak position (eV) FWHM (eV) Area Hf 4d 212.9 4.55 459.8 213.3 5.05 511.9 223.6 5.34 456.6 223.9 5.55 417.6 O 1s 529.5 3.07 293.4 529.8 3.05 241.7 532.6 8.56 248.3 532.5 7.54 157.5 3.3. Surface topography analysis The surface topography of HfO x thin films was characterized by atomic force microscopy (AFM) over a scanning area of 2 µm × 2 µm, and the images are shown in Fig. 4 . The AFM analysis reveals a smooth surface morphology across all samples, regardless of the P w . The average surface roughness showed a marginal variation in the range, 0.12–0.2 nm, indicating that plasma power has minimal influence on surface roughness, as also reported for carbon films [ 27 ]. At lower P w the limited energy leads to slower film growth with reduced adatom mobility, resulting in smoother surfaces. In contrast, at higher P w (2500 W), increased ion bombardment might introduce defects, leading to a marginal increase in roughness. However, the nominal variation in the roughness demonstrates that the films maintain a high degree of smoothness and uniformity across the P w range used in this study. 3.4. Silicon surface passivation The surface passivation quality of HfO x films was studied through minority carrier lifetime ( τ eff ) of the symmetric samples, HfO x /Si/HfO x . The overall quality of passivation was assessed using surface recombination velocity (SRV), which was determined through τ eff using the following Eq. ( 1 ). $$\:SRV=\frac{W}{{2\:\tau\:}_{eff}}$$ 1 where, W denotes wafer thickness and the factor 2 accounts for contributions from both front and rear surfaces. The τ eff and corresponding SRV of all samples are summarized in Table 2 . The as-deposited films exhibited poor surface passivation across all processing conditions. This lower passivation quality is attributed to the formation of poor interfacial oxide at the HfO x /Si interface, potentially resulting from the ionizing ultraviolet radiation generated during the oxygen plasma process. Also, interaction between reactive plasma species and surface atoms during film growth can rise the surface defect states [ 28 ]. Similar observations have been reported for SiO x , AlO x , and HfO x layers deposited on silicon substrates subjected to plasma radiation [ 29 , 30 ]. Rapid thermal annealing of the films at 400 ℃ under nitrogen ambient improved τ eff as presented in Table 2 . The observed enhancement in surface passivation is associated with the reduction in electrically active defects at the c-Si/HfO x interface. The annealing facilitates the migration of hydrogen atoms from hafnium oxide bulk towards the interface region, enabling them to chemically interact with dangling silicon bonds, thereby reducing defect related recombination [ 31 ]. In addition to chemical passivation, field-effect passivation suppresses surface recombination through electric fields induced by fixed charges within dielectric layer. Silicon surface inherently contains a high density of dangling bonds, which act as carrier recombination centers. These defects could be effectively passivated by the formation of an interfacial oxide layer. Additionally, fixed charges present at the oxide/silicon interface generate an electric field that repel minority charge carriers (electrons/holes) away from the interface, thereby reducing their probability of being trapped by surface defects. The effectiveness of chemical and field-effect passivation approaches is commonly evaluated by determining D it and Q eff as elaborated in the following sections. At a P w of 2500 W, the c-Si/HfO x interface exhibits improved passivation quality that is primarily attributed to chemical passivation mechanism, as evidenced by the measured D it of 3.28 × 10 12 cm − 2 eV − 1 . The HfO x layer contributes lower field effect passivation, which is associated with the presence of negative fixed charges at the interface typically on the order of 10¹² cm − 2 . Table 2 Effective minority carrier lifetime and calculated SRV values of the as deposited and annealed samples at P w range of 2000 W-2500 W. Plasma power ( P w ) As deposited τ eff (µs) S eff (cm/s) Annealed τ eff (µs) S eff (cm/s) 2000 5.41 3009 104 156.2 2200 5.10 3186 33 492.4 2400 5.11 3180 78 208.3 2500 5.90 2754 390 41.7 The interface is further characterized by C-V and G-V analyses as discussed in the following section. 3.5. Capacitance-Voltage analysis The passivation mechanism of the films was further evaluated through electrical measurements. The electrical characteristics of HfO x /n-Si MOS capacitors were studied using C-V analysis. Figure 5 shows high frequency (1MHz) C-V characteristics of HfO x /n-Si devices, where HfO x films were deposited at varying P w in the range of 2000 W-2500 W. The C-V spectra show a positive shift in the V fb from 0.29 V to 0.9 V with increasing P w , as summarised in Table 3 . The observed positive shift in V fb indicates the existence of negative fixed charges within HfO x film or at the HfO x /Si interface. The effective fixed charge density, Q eff was evaluated using the following relation, $$\:{V}_{fb}={\varphi\:}_{ms}-\frac{q{Q}_{eff}}{{C}_{ox}}$$ 2 where, \(\:{\varphi\:}_{ms}\) denotes the work function difference between the metal and the semiconductor, q is the elementary charge, and C ox is the capacitance of the dielectric layer. Correspondingly, Q eff shows a trend toward more negative values with increasing power. This behaviour could be due to a reduction in positively charged oxygen vacancies and a corresponding increase in negatively charged defects such as interstitial oxygen or hafnium vacancies in the oxide matrix. These defect mediated variations in the fixed charge are consistent with theoretical calculations reported for HfO₂ [ 32 ]. Further analysis of C-V characteristics was carried out to extract key electrical parameters, including V fb , Q eff , D it , barrier height ( φ B ), and depletion width ( W D ) at various P w , and the data is given in Table 4 . The doping concentration (N D for n-type) was evaluated from the slope of the linear region in C − 2 -V plot within the depletion regime [ 30 ]. Furthermore, D it at the HfOₓ/Si interface was evaluated using both C-V and G-V data. The Hill-Coleman method was used to calculate D it by analysing the frequency-dependent response of the interface traps, which manifest as deviations in the capacitance and conductance characteristics [ 33 ]. This method provides a reliable estimation of interface trap density, especially in the presence of energy-dispersive or slow traps as shown in Fig. 6 (a). Table 3 The electrical parameters extracted from C-V and G-V measurements at various P w used for HfO x deposition. Plasma Power (W) N D (×10 15 cm −3 ) ϕB (eV) WD (×10 5 cm) Qeff (×10 12 cm −2 ) Vfb (V) D it (×10 12 cm − 2 eV − 1 ) 2000 4.08 0.51 2.51 -0.96 0.29 7.55 2200 6.27 0.83 3.47 -1.49 0.58 9.88 2400 4.18 1.19 4.29 -1.76 0.76 8.82 2500 5.20 1.12 4.74 -2.78 0.90 3.28 The HfOₓ/n-Si interface was further studied, particularly in view of the high-quality effective lifetime achieved at a P w of 2500 W. The C-V and G-V measurements of HfOₓ/n-Si devices were used to analyse the frequency dependent response of the interface as shown in Figs. 6 (a) and 6 (b). The device exhibits frequency dispersion due to the interaction of interface trap states with the applied AC signal. At lower frequencies, these interface traps can effectively follow the AC modulation by trapping/emission of charge carriers. This dynamic behaviour resulted in increased capacitance in the accumulation region and induced a shift in V fb due to polarization effects [ 33 ]. The trapped charges modulate the depletion width, thereby altering the effective oxide capacitance. Conversely, at higher frequencies (> 100 kHz), the trap response time exceeds the AC signal period, rendering the traps electrically inactive. As a result, interface state contribution to the capacitance is suppressed, resulting in an observed lower capacitance. In MOS devices, the presence of interface states is manifested as a characteristic peak in the G-V response. However, for the HfOₓ/Si devices no such peak was observed, as shown in Fig. 6 (b), suggesting that the device response is governed by series resistance (Rₛ) rather than interface traps. The conductance of the device was further understood by evaluating Rₛ using the following equation, ​​ R s \(\:=\frac{{G}_{m}}{{G}_{m}^{2}+\:{\omega\:}^{2}{C}_{m}^{2}}\) (3) where G m and C m are the measured conductance and capacitance, and ω is the angular frequency of the applied AC signal. A pronounced frequency dependence of Rₛ is observed, as shown in Fig. 6 (c). This behaviour could be attributed to interface traps, which exhibit dispersive charging behaviour across the frequencies. The other contributing factors, including bulk semiconductor resistance, contact resistances at both the front and back interfaces and oxide interlayer resistances also play a significant role. These resistive components substantially affect the accuracy of the extracted C-V and G-V characteristics and must be considered to interpret the electrical response of the device. The presence of R s introduces an additional voltage drop across the device, which results in a shift of the V fb and alters the depletion region width. These effects modify the overall capacitance behaviour of the device, particularly in the depletion and inversion regimes, thereby affecting the accuracy of the measured electrical characteristics. Owing to the significant magnitude of Rₛ , the contribution of interface states is largely suppressed and impact of R s becomes even more pronounced. This leads to inaccurate estimation of device parameters at higher frequencies (1 MHz). Therefore, correction for R s is essential to evaluate the device characteristics accurately, which was done based on the method detailed by Nicollian and Brews [ 34 ], using the relations, $$\:\text{C}c=\frac{{G}_{m}^{2}}{{G}_{m}^{2}+\:{\omega\:}^{2}{C}_{m}^{2}}$$ 4 $$\:{G}_{c}=\frac{\left[{G}_{m}^{2}+{\left(\omega\:{c}_{m}\right)}^{2}\right]a}{{\left(\omega\:{c}_{m}\right)}^{2}+{a}^{2}}$$ 5 $$\:a={G}_{m}-\left[{G}_{m}^{2}+{\left(w{C}_{m}\right)}^{2}\right]{R}_{s}$$ 6 where C m and G m are the measured values, and C c and G c are the corresponding corrected capacitance and conductance. Figure 7 presents the C-V and G-V curves before and after eliminating the influence of series resistance. Compared to the experimental data, C c shows an increase, while G c exhibits a reduction, displaying a characteristic peak attributed to interface traps in the depletion zone. This indicates that the influence of surface state losses is significantly dominated by the series resistance ( R s ). 3.6. Impedance Spectroscopy Impedance spectroscopy (IS) was used to investigate the impedance behaviour of the metal/HfOₓ/n-Si MOS structure. The resulting Cole-Cole plots measured at different dc bias voltages are shown in Fig. 8 . The Z′-axis represents the real part of impedance associated with the shunt/recombination resistance, while the Z″-axis corresponds to the imaginary part is related to the capacitive reactance arising from the junction/trap capacitance [ 12 ]. As illustrated in Fig. 8 , all impedance spectra exhibit a semi-circular arc, which is characteristic of a system that could be modelled by a resistor-capacitor (RC) equivalent circuit. This confirms that the MOS structure exhibits both resistive and capacitive behaviour. The frequency dependent impedance of the MOS structure is represented as, $$\:Z\:\left(\omega\:\right)={Z}^{{\prime\:}}\left(w\right)+j{Z}^{{\prime\:}{\prime\:}}\left(\omega\:\right)$$ 7 where ω is the angular frequency, \(\:{Z}^{{\prime\:}}\) and \(\:{Z}^{{\prime\:}{\prime\:}}\) denotes the real and imaginary components of the impedance respectively. $$\:{Z}^{{\prime\:}}=\frac{{R}_{ox}}{1+{\left(\omega\:{R}_{ox}{C}_{ox}\right)}^{2}}+\frac{{R}_{X}}{1+{\left(\omega\:{R}_{X}{C}_{X}\right)}^{2}}+{R}_{s}$$ 8 $$\:{Z}^{{\prime\:}{\prime\:}}=-\frac{\omega\:{R}_{ox}^{2}{C}_{ox}}{1+{\left(\omega\:{R}_{ox}{C}_{ox}\right)}^{2}}-\frac{\omega\:{R}_{X}^{2}{C}_{X}}{1+{\left(\omega\:{R}_{X}{C}_{X}\right)}^{2}}+\omega\:L$$ 9 The diameter of the semicircle in the Cole–Cole plot varies with the applied gate voltage, reflecting the corresponding changes in the total impedance of the device. In the inversion regime, as the gate voltage increases from 0.4 V to 1.2 V, the semicircle expands along the real axis (Z′), indicating an increase in shunt (recombination) resistance from ~ 170 MΩ to 200 MΩ. This is consistent with the widening of depletion region as the reverse bias increases, which reduces the recombination rate by spatially separating the charge carriers. As the gate voltage is further increased to -1.6 V, the shunt resistance decreases to 165 MΩ. This reduction signifies the transition into the deep inversion regime, where the formation of a dense inversion layer dominates the electrical response. The increased density of mobile holes in the inversion layer enhances the conductivity near the surface, thereby lowering the recombination resistance. Table 4 Fitting parameters extracted from the impedance spectra shown in Fig. 8 using the equivalent RC circuit model depicted in the inset. Here R and C describe the resistance and capacitance, respectively, associated with the HfO x /Si interface. Voltage (V) R (MΩ) C (pF) -1.6 165.5 ± 1.21 165.6 ± 0.53 -1.4 180.1 ± 1.33 164.9 ± 0.51 -1.2 200.6 ± 1.52 161.5 ± 0.48 -0.8 188.1 ± 1.65 165.8 ± 0.51 -0.4 170.2 ± 1.30 169.8 ± 0.54 4. Conclusions HfO x thin films were deposited by PEALD at different plasma powers ( P w ) in order to assess their passivation quality on crystalline silicon. Effective passivation of c-Si surfaces achieved using HfO x thin films at an optimum power of 2500 W, followed by an activation anneal at 400° C under nitrogen ambient, which preserved the amorphous nature of HfO x films. AFM analysis showed that HfO x films were exceptionally smooth with an average roughness below 2 Å. FTIR analysis indicated the formation of an interfacial layer comprising a mixed SiOₓ and HfO x phase, resulting from interfacial reactions during film deposition. XPS analysis revealed that increasing deposition power to 2500 W reduced oxygen-related defect states in HfO x films. C-V analysis revealed that chemical passivation has been the dominant mechanism contributing to the improved interface quality. This was supported by lower D it of 3.28 × 10 12 cm − 2 eV − 1 at the HfO x /Si interface, and moderate fixed charge densities, indicating a limited contribution from filed effect passivation. As a result, an SRV less than 45 cm/s was achieved for the film thickness of 16 nm on n-type silicon substrates. The corrected C-V and G-V analyses further highlighted impact of series resistance ( Rₛ ), which must be accounted for to accurately assess device characteristics. Impedance spectroscopy confirmed the RC behaviour of the MOS structure, with bias-dependent trends revealing changes in recombination resistance across inversion and depletion regimes. The results demonstrate the potential of amorphous HfO x films deposited by PEALD as a promising passivation layer for high-efficiency silicon-based electronic and photovoltaic devices. Declarations Author contributions Rinki: Writing - original draft, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Meenakshi: Formal analysis, Data curation, Conceptualization. Paras: Formal analysis, Investigation. Anil: Formal analysis, Investigation. Shivanshu: Formal analysis, Investigation. Uttam Kumar Goutam : Formal analysis, Investigation Mrinal Dutta: Software, Resources, Formal analysis, Investigation. Sanjay K. Srivastava: Formal analysis, Investigation. Paramita Guha: Formal analysis, Investigation Prathap Pathi: Writing-review & editing, Supervision, Formal analysis, Conceptualization, Resources, Methodology, Investigation, Funding acquisition. Data availability All data generated or analyzed during this study are included in this article. Competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements The authors are thankful to CSIR-National Physical Laboratory, New Delhi, for providing the research facilities, Council of Scientific and Industrial Research (CSIR), for fellowship support (Grant No. 31/0001(15737)/2022-EMR-I). This work is partly supported by the project (Ref. No. CPRI/R&D/TC/GDEC/2024) sponsored by MNRE, Govt. of India. References Gope, J., Batra, N., Panigrahi, J., Singh, R., Maurya, K. K., Srivastava, R., & Singh, P. K. (2015). Silicon surface passivation using thin HfO2 films by atomic layer deposition. Applied Surface Science, 357, 635-642. Muduli, S. P., & Kale, P. (2023). State-of-the-art passivation strategies of c-Si for photovoltaic applications: A review. Materials Science in Semiconductor Processing , 154 , 107202. Aber, A. G., Glunz, S., & Warta, W. 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1","display":"","copyAsset":false,"role":"figure","size":46189,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Film thickness and (b) refractive index of the PEALD-grown HfO\u003csub\u003ex \u003c/sub\u003efilms deposited at different \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e in the range of 2000 W-2500 W\u003cstrong\u003e.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8590256/v1/e84967c90171de5435c06d24.jpg"},{"id":100950563,"identity":"23de9e8d-d432-4170-b831-1c8297e08d8b","added_by":"auto","created_at":"2026-01-23 07:08:36","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":93437,"visible":true,"origin":"","legend":"\u003cp\u003e(a) GIXRD and (b) FTIR spectra of HfO\u003csub\u003ex\u003c/sub\u003e films deposited on n-Si substrates at various \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e, respectively.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8590256/v1/3bb8b21baeb12e2081a3c99b.jpg"},{"id":100881305,"identity":"1dbe7988-37e7-47c3-846b-3ebe091599c3","added_by":"auto","created_at":"2026-01-22 11:13:03","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":143853,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of (a) Hf 4d and (b) O 1s of HfO\u003csub\u003ex\u003c/sub\u003e films prepared at the \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e of 2000 W and 2500 W.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8590256/v1/2823c75b36fac645dd1dd701.jpg"},{"id":100881299,"identity":"6a4cd0cc-e9a3-4d9f-aa79-bf46ac4a53d9","added_by":"auto","created_at":"2026-01-22 11:13:03","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":79216,"visible":true,"origin":"","legend":"\u003cp\u003eAFM image of HfO\u003csub\u003ex\u003c/sub\u003e films deposited at different plasma powers of (a) 2000 W, (b) 2200 W, and (c) 2400 W (d) 2500 W. The inset shows the plasma power and corresponding average surface roughness (R\u003csub\u003ea\u003c/sub\u003e) of the film.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8590256/v1/442433a8993f3fb631f107a7.jpg"},{"id":101202482,"identity":"3078b62b-ba16-4b57-96e4-8661ba33f599","added_by":"auto","created_at":"2026-01-27 09:34:39","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":38399,"visible":true,"origin":"","legend":"\u003cp\u003eNormalized capacitance- voltage characteristics of HfO\u003csub\u003ex\u003c/sub\u003e/n-Si devices with HfO\u003csub\u003ex\u003c/sub\u003e films deposited at different \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e. The measurements were performed at the frequency of 1MHz.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8590256/v1/4d544bf9b34ca67cca434c68.jpg"},{"id":100881337,"identity":"18e86e8d-67db-4fc7-a3aa-5a69ee28e817","added_by":"auto","created_at":"2026-01-22 11:13:10","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":56759,"visible":true,"origin":"","legend":"\u003cp\u003e(a) C-V (b) G-V and (c) R-V characteristics of HfO\u003csub\u003ex\u003c/sub\u003e/Si device at different frequencies for the HfO\u003csub\u003ex\u003c/sub\u003e film deposited at a \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e of 2500W.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8590256/v1/a5c6561252159839b97ce53b.jpg"},{"id":100949794,"identity":"bc0efe74-8920-464c-9b91-79544b04c2e0","added_by":"auto","created_at":"2026-01-23 07:05:41","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":48500,"visible":true,"origin":"","legend":"\u003cp\u003eMeasured and corrected (a) capacitance and (b) conductance spectra at 1 MHz for the HfO\u003csub\u003eX\u003c/sub\u003e/n-Si devices obtained after eliminating the influence of series resistance \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e. The HfO\u003csub\u003ex\u003c/sub\u003e film was deposited at \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e of 2500 W.\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8590256/v1/8661c438688d9a5171faa1be.jpg"},{"id":100881312,"identity":"9814f76b-9933-4e86-aef1-61e3d3ac72c0","added_by":"auto","created_at":"2026-01-22 11:13:04","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":39522,"visible":true,"origin":"","legend":"\u003cp\u003eComplex impedance spectra of the Al/HfO\u003csub\u003ex\u003c/sub\u003e/Si device under different dc bias voltages. The HfOx was deposited at the plasma power 2500 W and inset shows the corresponding equivalent circuit model used to interpret the impedance data.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8590256/v1/cc17b153483252c4a9a0e338.jpg"},{"id":101207649,"identity":"422a5fff-5ea2-4694-8f1f-94fec8c2d172","added_by":"auto","created_at":"2026-01-27 10:06:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1531881,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8590256/v1/27c49279-725f-4b2d-ae13-655c9b7a7f20.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003e\u003cstrong\u003ePlasma-Enhanced ALD of HfO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ex\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e for Effective Surface Passivation of Silicon: A Material and Interface Study\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eOne of the effective strategies to lower solar cell fabrication costs is to lower the thickness of crystalline silicon (c-Si) substrates, thereby minimizing material usage. However, thinner wafers are more susceptible to charge carrier recombination at the surfaces, which degrades the device performance. Consequently, effective suppression of surface recombination is essential for maintaining high efficiency and ensuring cost-effective production of industrial silicon photovoltaics [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe process of minimizing charge carrier recombination at the crystalline silicon (c-Si) surface is known as \u0026ldquo;surface passivation\u0026rdquo;. This is typically achieved using a dielectric thin film that mitigates recombination losses either by chemically terminating dangling bonds, thereby reducing the \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e (chemical passivation) or/and by using built-in fixed charges that repel one type of charge carrier (electron or hole) away from the surface, referred to as field effect passivation [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA wide range of dielectric materials has been explored in recent past to mitigate defect-assisted Shockley-Read Hall (SRH) recombination, including Al-doped ZnO [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], TiO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], ZrO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], SiO\u003csub\u003ex\u003c/sub\u003e [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], SiN\u003csub\u003ex\u003c/sub\u003e [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], a-Si:H [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], ZnO, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], and HfO\u003csub\u003ex\u003c/sub\u003e [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Amongst these materials, hafnium oxide (HfO\u003csub\u003ex\u003c/sub\u003e) is of particular interest, especially in microelectronics, due to its exceptional electrical and optical properties, including a high dielectric constant (k\u0026thinsp;=\u0026thinsp;16\u0026ndash;25), a wide bandgap (5.6\u0026ndash;5.8 eV), a refractive index of approximately 2-2.1 and excellent thermal and chemical stability with silicon. Its optical transmittance in the visible range makes HfO\u003csub\u003ex\u003c/sub\u003e a promising material for use in high-k gate dielectrics, surface passivation layers and antireflection coatings (ARCs) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, the deposition method HfO\u003csub\u003ex\u003c/sub\u003e plays a key role in determining the effectiveness of passivation quality of the resulting layers. ALD has gained considerable attention for depositing conformal and ultrathin dielectric films with precise thickness control [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. PEALD offers advantages over thermal ALD, including enhanced film quality at lower deposition temperatures [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], which arises from the high reactivity of plasma-generated species. In addition, PEALD enables access to a broader processing parameter window such as increased growth rates per cycle, better control over stoichiometry and composition, compatibility with a wide range of precursors, and superior film characteristics at lower processing temperatures that are often unattainable using thermally driven ALD processes. These features make PEALD a promising method for the deposition of high-quality HfO\u003csub\u003ex\u003c/sub\u003e films with improved electrical and interface properties on silicon substrates.\u003c/p\u003e \u003cp\u003eDespite its potential, the application of PEALD-deposited HfO\u003csub\u003ex\u003c/sub\u003e for silicon surface passivation remains relatively underexplored. Only a few studies have evaluated its effectiveness in enhancing minority carrier lifetime. Meenakshi et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] reported SRV of approximately 10 cm/s for HfOₓ films with a thickness of ~\u0026thinsp;23 nm deposited on p-type silicon substrates. Rajbir et al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] achieved SRV below 40 cm/s using PEALD-grown HfO\u003csub\u003ex\u003c/sub\u003e on n-type silicon. Zhang et al. investigated the influence of oxygen plasma pre-treatment followed by subsequent annealing reporting an improved minority carrier lifetime of 67 \u0026micro;s [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Ailish et al. showed that a 12 nm thick HfO\u003csub\u003ex\u003c/sub\u003e layer on n-Si could yield an SRV as low as 4.1 cm/s [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eGiven these promising yet limited findings, this work systematically investigates the passivation mechanisms of PEALD-deposited HfO\u003csub\u003ex\u003c/sub\u003e on n-type substrates, with an emphasis on optimizing the \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e for achieving high quality minority carrier lifetime at lower film thickness. The effectiveness of surface passivation has been evaluated through minority carrier lifetime measurements and explored the underlying HfO\u003csub\u003ex\u003c/sub\u003e passivation mechanism as a function of \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e, which modulates \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e at the interface of HfO\u003csub\u003ex\u003c/sub\u003e/Si. The interface characteristics have been analysed using capacitance and conductance measurements. The results were analysed in detail to provide insights into optimizing HfO\u003csub\u003ex\u003c/sub\u003e based dielectric layers for silicon photovoltaics.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Sample preparation\u003c/h2\u003e \u003cp\u003eSurface passivation was examined using moderately doped float-zone n-Si substrates (\u0026lt;\u0026thinsp;100\u0026gt;, 0.5-4 Ω-cm, 350\u0026thinsp;\u0026plusmn;\u0026thinsp;25 \u0026micro;m). All samples underwent standard RCA cleaning procedures (SC-I and SC-II) before being introduced into reaction chamber.\u003c/p\u003e \u003cp\u003ePEALD of HfO\u003csub\u003ex\u003c/sub\u003e was carried out using (M/s Picosun, Model R200) reactor equipped with a remote plasma source (M/s Advanced Energy). The films were deposited using tetrakisethyl-methyl-amino)hafnium [TEMAHf, Hf(N(C₂H₅)(CH₃))₄] as the hafnium precursor and oxygen plasma as oxidizing agent. Each ALD cycle included two half-cycles: one for TEMAHf exposure and one for O₂ plasma exposure, separated by nitrogen purging steps to eliminate unreacted precursors and byproducts. To maintain efficient precursor delivery, TEMAHf source was maintained at 120\u0026deg;C to compensate for its low vapor pressure, while delivery lines were maintained at 150\u0026deg;C to prevent condensation. The films were deposited at varying \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e in the range of 2000 W \u0026minus;\u0026thinsp;2500 W.\u003c/p\u003e \u003cp\u003eAll the samples were subjected to rapid thermal annealing (Model: AS-one 150, M/s Annealsys, France) at 400\u0026deg;C for 12 minutes under nitrogen ambient to enhance surface passivation. For electrical measurements, metal-oxide-semiconductor (MOS) structures were fabricated by thermally evaporating aluminium contacts (1 mm diameter) onto the HfO\u003csub\u003ex\u003c/sub\u003e surface, while rear surface was fully coated with aluminum.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Measurement techniques\u003c/h2\u003e \u003cp\u003eFilm thickness was measured using a spectroscopic ellipsometer (VASE, model: M2000, M/s J.A. Wollam Company. Inc., USA). Structural analysis was carried out using GIXRD (Model: PAN analytical Xpert PRO MRD), operated in grazing incidence mode at a fixed incidence angle of 1\u0026deg;. Interfacial layer formation and bonding characteristics were investigated using fourier transform infrared spectroscopy (FTIR) (Model 2000, M/s Perkin Elmer spectrometer, USA). Surface morphology of the HfOx films was studied using atomic force microscope (AFM, Multimode V, Veeco Instruments) measurements.\u003c/p\u003e \u003cp\u003eX-ray photoelectron spectroscopy (XPS) measurements were performed at the hard X-ray photoelectron spectroscopy (HAXPES) beamline BL-14 of the indus-2 synchrotron facility, Indore, India. The beamline is equipped with a Si (111) double crystal monochromator (DCM) and a PHOIBOS 225 electron energy analyzer (Specs). The measurements were conducted using incident X-ray photons with an energy of 4065 eV. The τ\u003csub\u003eeff\u003c/sub\u003e was measured with the sinton lifetime tester based on photoconductance decay (Model: WCT-120). Electrical measurements were carried out on MOS structures using gamry instruments (Gamry Reference 600 Potentiostat/Galvanostat/ZRA, Inc., USA). A 10 mV AC voltage signal was applied along with DC bias to meet small-signal requirements for accurate measurements of oxide capacitance.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Film thickness\u003c/h2\u003e \u003cp\u003eThe HfOₓ film thickness and refractive index were extracted from ellipsometry measurements performed at three incident angles (65\u0026deg;, 70\u0026deg;, and 75\u0026deg;), over a wavelength range of 245\u0026ndash;1700 nm. The thickness of HfO\u003csub\u003ex\u003c/sub\u003e was found to depend on the applied \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a), the extracted thickness exhibits a non-linear relationship between the film thickness and \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e, where thickness initially decreases as \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e increases from 2000 W to 2200 W, and then increases at higher power. This behaviour suggests a transition in growth mechanism, which could be due to competing surface reactions at higher plasma energies [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe refractive index spectra, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b) exhibit normal dispersion behaviour across wavelength range of 245\u0026ndash;1700 nm with minimal variation for the films deposited at different \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e. This indicates that the optical properties remain consistent despite variations in deposition conditions. The films exhibited a refractive index of approximately 2 at a wavelength of 632.8 nm, with a variation in band gap from 5.3 eV to 5.6 eV in studied \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e range. The results are in good agreement with earlier studies reported on ALD-grown HfO₂ thin films [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e3.2. Film crystallinity and composition\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eThe structural properties of HfO\u003csub\u003ex\u003c/sub\u003e thin films were investigated using GIXRD. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a) shows the GIXRD spectra of the films deposited at different \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e. The absence of distinct diffraction peaks related to HfO\u003csub\u003ex\u003c/sub\u003e indicates that the deposited films are amorphous. However, a prominent peak observed at 52\u0026deg;, accompanied by a hump at 54\u0026deg;, is associated with the silicon substrate beneath the film [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. As can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a), higher power (2500 W) during the deposition enhances the growth rate and density of the HfO\u003csub\u003ex\u003c/sub\u003e film, leading to a better coverage of the silicon substrate. This improved coverage further reduces the penetration of X-rays to the silicon substrate, reducing the silicon substrate peak intensity at 2500 W power. HfO\u003csub\u003ex\u003c/sub\u003e is known to exhibit multiple crystalline phases, such as monoclinic, orthorhombic, and tetragonal phases. In general, the crystallinity of thin film is influenced by several parameters, including deposition method, substrate temperature and post-deposition annealing (PDA) conditions. PEALD is a low-temperature process often results in amorphous films. However, after upon PDA, crystalline phases could emerge depending on the annealing conditions.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1. FTIR analysis\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (b) shows the FTIR spectra of HfO\u003csub\u003ex\u003c/sub\u003e films deposited at various \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e. The peak observed in the wavenumber range, 550\u0026ndash;650 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is associated with Hf-O vibrational modes. Additionally, signal near 610 cm⁻\u0026sup1; arises from Si-Si vibrational mode from the substrate [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The peak at 738 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the monoclinic phase of HfO\u003csub\u003ex\u003c/sub\u003e, while the broad absorption around 890 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is associated with Si-H bonds. Peaks observed in the 1000\u0026ndash;1200 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e range and at 816 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to Si-O stretching vibrations, indicating that oxygen from the plasma or the Hf precursor reacted with the silicon substrate during deposition, forming a thin interfacial SiO\u003csub\u003e2\u003c/sub\u003e​ layer. The peak observed at 967 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is associated with the formation of a thin Hf-Si-O interfacial layer (IL), which could be developed during hafnium oxide deposition. Similar observations were reported for HfO\u003csub\u003e2\u003c/sub\u003e films deposited by UV-photo-CVD [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The FTIR analysis further indicates that there are no distinct changes in the functional groups of the layers or at the interface with varying \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2. X-ray photoelectron spectroscopy\u003c/h2\u003e \u003cp\u003eX-ray photoelectron spectroscopy (XPS) was performed to investigate the chemical bonding states of the HfO\u003csub\u003ex\u003c/sub\u003e thin films. The binding energy scale was calibrated using the C 1s peak positioned at 284.8 eV as an internal reference. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (a) shows the Hf 4d core-level spectra for the films deposited at \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e of 2000 W and 2500 W. Two distinct peaks are observed at the binding energies of 213.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4 eV and 223.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 eV corresponding to Hf 4d₅/₂ and Hf 4d₃/₂, respectively. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (b) shows the O 1s core-level spectrum, which is deconvoluted into two peaks, O\u003csub\u003eI\u003c/sub\u003e at 529.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 eV corresponds to Hf-O bonds in HfO\u003csub\u003ex\u003c/sub\u003e, while O\u003csub\u003eII\u003c/sub\u003e around 532.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 eV is attributed to surface hydroxyl (-OH) groups or oxygen-related defects [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Although no significant shift in the binding energies of these peaks is observed with increasing deposition power, a noticeable reduction in the O\u003csub\u003eII\u003c/sub\u003e (532.5 eV) peak area (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) at 2500 W indicates a decrease in defect-related oxygen species. This reduction correlates with the improved passivation behavior observed in the C-V measurements, suggesting that oxygen-deficient and hydroxyl-related defects are effectively suppressed at higher deposition power. The XPS spectral parameters corresponding to the O 1s and Hf 4d core levels are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eXPS peak fit parameters corresponding to Hf 4d and O 1s.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePower (W)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2500\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePeak position(eV)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFWHM (eV)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePeak position (eV)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFWHM (eV)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHf 4d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e212.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e459.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e213.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e511.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e223.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e456.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e223.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e417.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO 1s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e529.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e293.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e529.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e241.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e532.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e248.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e532.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e157.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Surface topography analysis\u003c/h2\u003e \u003cp\u003eThe surface topography of HfO\u003csub\u003ex\u003c/sub\u003e thin films was characterized by atomic force microscopy (AFM) over a scanning area of 2 \u0026micro;m \u0026times; 2 \u0026micro;m, and the images are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The AFM analysis reveals a smooth surface morphology across all samples, regardless of the \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e. The average surface roughness showed a marginal variation in the range, 0.12\u0026ndash;0.2 nm, indicating that plasma power has minimal influence on surface roughness, as also reported for carbon films [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. At lower \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e the limited energy leads to slower film growth with reduced adatom mobility, resulting in smoother surfaces. In contrast, at higher \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e (2500 W), increased ion bombardment might introduce defects, leading to a marginal increase in roughness. However, the nominal variation in the roughness demonstrates that the films maintain a high degree of smoothness and uniformity across the \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e range used in this study.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.4. Silicon surface passivation\u003c/h2\u003e \u003cp\u003eThe surface passivation quality of HfO\u003csub\u003ex\u003c/sub\u003e films was studied through minority carrier lifetime (\u003cem\u003eτ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e) of the symmetric samples, HfO\u003csub\u003ex\u003c/sub\u003e/Si/HfO\u003csub\u003ex\u003c/sub\u003e. The overall quality of passivation was assessed using surface recombination velocity (SRV), which was determined through \u003cem\u003eτ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e using the following Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:SRV=\\frac{W}{{2\\:\\tau\\:}_{eff}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere, \u003cem\u003eW\u003c/em\u003e denotes wafer thickness and the factor 2 accounts for contributions from both front and rear surfaces.\u003c/p\u003e \u003cp\u003eThe \u003cem\u003eτ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e and corresponding SRV of all samples are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The as-deposited films exhibited poor surface passivation across all processing conditions. This lower passivation quality is attributed to the formation of poor interfacial oxide at the HfO\u003csub\u003ex\u003c/sub\u003e/Si interface, potentially resulting from the ionizing ultraviolet radiation generated during the oxygen plasma process. Also, interaction between reactive plasma species and surface atoms during film growth can rise the surface defect states [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Similar observations have been reported for SiO\u003csub\u003ex\u003c/sub\u003e, AlO\u003csub\u003ex\u003c/sub\u003e, and HfO\u003csub\u003ex\u003c/sub\u003e layers deposited on silicon substrates subjected to plasma radiation [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRapid thermal annealing of the films at 400 ℃ under nitrogen ambient improved \u003cem\u003eτ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e as presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The observed enhancement in surface passivation is associated with the reduction in electrically active defects at the c-Si/HfO\u003csub\u003ex\u003c/sub\u003e interface. The annealing facilitates the migration of hydrogen atoms from hafnium oxide bulk towards the interface region, enabling them to chemically interact with dangling silicon bonds, thereby reducing defect related recombination [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn addition to chemical passivation, field-effect passivation suppresses surface recombination through electric fields induced by fixed charges within dielectric layer. Silicon surface inherently contains a high density of dangling bonds, which act as carrier recombination centers. These defects could be effectively passivated by the formation of an interfacial oxide layer. Additionally, fixed charges present at the oxide/silicon interface generate an electric field that repel minority charge carriers (electrons/holes) away from the interface, thereby reducing their probability of being trapped by surface defects.\u003c/p\u003e \u003cp\u003eThe effectiveness of chemical and field-effect passivation approaches is commonly evaluated by determining \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eQ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e as elaborated in the following sections. At a \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e of 2500 W, the c-Si/HfO\u003csub\u003ex\u003c/sub\u003e interface exhibits improved passivation quality that is primarily attributed to chemical passivation mechanism, as evidenced by the measured \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e of 3.28 \u0026times; 10\u003csup\u003e12\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e eV\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The HfO\u003csub\u003ex\u003c/sub\u003e layer contributes lower field effect passivation, which is associated with the presence of negative fixed charges at the interface typically on the order of 10\u0026sup1;\u0026sup2; cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eEffective minority carrier lifetime and calculated SRV values of the as deposited and annealed samples at \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e range of 2000 W-2500 W.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlasma power (\u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAs deposited\u003c/p\u003e \u003cp\u003e\u003cem\u003eτ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e (\u0026micro;s)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eS\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e (cm/s)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAnnealed\u003c/p\u003e \u003cp\u003e\u003cem\u003eτ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e (\u0026micro;s)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eS\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003cp\u003e(cm/s)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e104\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e156.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3186\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e492.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e208.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2754\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e390\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e41.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe interface is further characterized by C-V and G-V analyses as discussed in the following section.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.5. Capacitance-Voltage analysis\u003c/h2\u003e \u003cp\u003eThe passivation mechanism of the films was further evaluated through electrical measurements. The electrical characteristics of HfO\u003csub\u003ex\u003c/sub\u003e/n-Si MOS capacitors were studied using C-V analysis. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows high frequency (1MHz) C-V characteristics of HfO\u003csub\u003ex\u003c/sub\u003e/n-Si devices, where HfO\u003csub\u003ex\u003c/sub\u003e films were deposited at varying \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e in the range of 2000 W-2500 W. The C-V spectra show a positive shift in the \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003efb\u003c/em\u003e\u003c/sub\u003e from 0.29 V to 0.9 V with increasing \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e, as summarised in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The observed positive shift in \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003efb\u003c/em\u003e\u003c/sub\u003e indicates the existence of negative fixed charges within HfO\u003csub\u003ex\u003c/sub\u003e film or at the HfO\u003csub\u003ex\u003c/sub\u003e/Si interface. The effective fixed charge density, \u003cem\u003eQ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e was evaluated using the following relation,\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{V}_{fb}={\\varphi\\:}_{ms}-\\frac{q{Q}_{eff}}{{C}_{ox}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\varphi\\:}_{ms}\\)\u003c/span\u003e\u003c/span\u003e denotes the work function difference between the metal and the semiconductor, \u003cem\u003eq\u003c/em\u003e is the elementary charge, and \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003eox\u003c/em\u003e\u003c/sub\u003e is the capacitance of the dielectric layer. Correspondingly, \u003cem\u003eQ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e shows a trend toward more negative values with increasing power. This behaviour could be due to a reduction in positively charged oxygen vacancies and a corresponding increase in negatively charged defects such as interstitial oxygen or hafnium vacancies in the oxide matrix. These defect mediated variations in the fixed charge are consistent with theoretical calculations reported for HfO₂ [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFurther analysis of C-V characteristics was carried out to extract key electrical parameters, including \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003efb\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eQ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e, barrier height (\u003cem\u003eφ\u003c/em\u003e\u003csub\u003e\u003cem\u003eB\u003c/em\u003e\u003c/sub\u003e), and depletion width (\u003cem\u003eW\u003c/em\u003e\u003csub\u003e\u003cem\u003eD\u003c/em\u003e\u003c/sub\u003e) at various \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e, and the data is given in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The doping concentration (N\u003csub\u003eD\u003c/sub\u003e for n-type) was evaluated from the slope of the linear region in \u003cem\u003eC\u003c/em\u003e\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e-V plot within the depletion regime [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Furthermore, \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e at the HfOₓ/Si interface was evaluated using both C-V and G-V data. The Hill-Coleman method was used to calculate \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e by analysing the frequency-dependent response of the interface traps, which manifest as deviations in the capacitance and conductance characteristics [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. This method provides a reliable estimation of interface trap density, especially in the presence of energy-dispersive or slow traps as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (a).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe electrical parameters extracted from C-V and G-V measurements at various \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e used for HfO\u003csub\u003ex\u003c/sub\u003e deposition.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlasma Power (W)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eD\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003cp\u003e(\u0026times;10\u003csup\u003e15\u003c/sup\u003ecm\u003csup\u003e\u0026minus;3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eϕB\u003c/em\u003e\u003c/p\u003e \u003cp\u003e(eV)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eWD\u003c/em\u003e\u003c/p\u003e \u003cp\u003e(\u0026times;10\u003csup\u003e5\u003c/sup\u003ecm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eQeff\u003c/em\u003e\u003c/p\u003e \u003cp\u003e(\u0026times;10\u003csup\u003e12\u003c/sup\u003ecm\u003csup\u003e\u0026minus;2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eVfb\u003c/em\u003e\u003c/p\u003e \u003cp\u003e(V)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003cp\u003e(\u0026times;10\u003csup\u003e12\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e eV\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-1.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e9.88\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-1.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e8.82\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-2.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e3.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe HfOₓ/n-Si interface was further studied, particularly in view of the high-quality effective lifetime achieved at a \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e of 2500 W. The C-V and G-V measurements of HfOₓ/n-Si devices were used to analyse the frequency dependent response of the interface as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (a) and 6 (b). The device exhibits frequency dispersion due to the interaction of interface trap states with the applied AC signal. At lower frequencies, these interface traps can effectively follow the AC modulation by trapping/emission of charge carriers. This dynamic behaviour resulted in increased capacitance in the accumulation region and induced a shift in \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003efb\u003c/em\u003e\u003c/sub\u003e due to polarization effects [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The trapped charges modulate the depletion width, thereby altering the effective oxide capacitance. Conversely, at higher frequencies (\u0026gt;\u0026thinsp;100 kHz), the trap response time exceeds the AC signal period, rendering the traps electrically inactive. As a result, interface state contribution to the capacitance is suppressed, resulting in an observed lower capacitance.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn MOS devices, the presence of interface states is manifested as a characteristic peak in the G-V response. However, for the HfOₓ/Si devices no such peak was observed, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (b), suggesting that the device response is governed by series resistance (Rₛ) rather than interface traps. The conductance of the device was further understood by evaluating Rₛ using the following equation,\u003c/p\u003e \u003cp\u003e​​ \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:=\\frac{{G}_{m}}{{G}_{m}^{2}+\\:{\\omega\\:}^{2}{C}_{m}^{2}}\\)\u003c/span\u003e\u003c/span\u003e (3)\u003c/p\u003e \u003cp\u003ewhere \u003cem\u003eG\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e are the measured conductance and capacitance, and \u003cem\u003eω\u003c/em\u003e is the angular frequency of the applied AC signal. A pronounced frequency dependence of \u003cem\u003eRₛ\u003c/em\u003e is observed, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (c). This behaviour could be attributed to interface traps, which exhibit dispersive charging behaviour across the frequencies. The other contributing factors, including bulk semiconductor resistance, contact resistances at both the front and back interfaces and oxide interlayer resistances also play a significant role. These resistive components substantially affect the accuracy of the extracted C-V and G-V characteristics and must be considered to interpret the electrical response of the device.\u003c/p\u003e \u003cp\u003eThe presence of \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e introduces an additional voltage drop across the device, which results in a shift of the \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003efb\u003c/em\u003e\u003c/sub\u003e and alters the depletion region width. These effects modify the overall capacitance behaviour of the device, particularly in the depletion and inversion regimes, thereby affecting the accuracy of the measured electrical characteristics. Owing to the significant magnitude of \u003cem\u003eRₛ\u003c/em\u003e, the contribution of interface states is largely suppressed and impact of \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e becomes even more pronounced. This leads to inaccurate estimation of device parameters at higher frequencies (1 MHz). Therefore, correction for \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e is essential to evaluate the device characteristics accurately, which was done based on the method detailed by Nicollian and Brews [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], using the relations,\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:\\text{C}c=\\frac{{G}_{m}^{2}}{{G}_{m}^{2}+\\:{\\omega\\:}^{2}{C}_{m}^{2}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\:{G}_{c}=\\frac{\\left[{G}_{m}^{2}+{\\left(\\omega\\:{c}_{m}\\right)}^{2}\\right]a}{{\\left(\\omega\\:{c}_{m}\\right)}^{2}+{a}^{2}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ5\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ5\" name=\"EquationSource\"\u003e\n$$\\:a={G}_{m}-\\left[{G}_{m}^{2}+{\\left(w{C}_{m}\\right)}^{2}\\right]{R}_{s}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e6\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eG\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e are the measured values, and \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eG\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e are the corresponding corrected capacitance and conductance. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e presents the C-V and G-V curves before and after eliminating the influence of series resistance. Compared to the experimental data, C\u003csub\u003ec\u003c/sub\u003e shows an increase, while G\u003csub\u003ec\u003c/sub\u003e exhibits a reduction, displaying a characteristic peak attributed to interface traps in the depletion zone. This indicates that the influence of surface state losses is significantly dominated by the series resistance (\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.6. Impedance Spectroscopy\u003c/h2\u003e \u003cp\u003eImpedance spectroscopy (IS) was used to investigate the impedance behaviour of the metal/HfOₓ/n-Si MOS structure. The resulting Cole-Cole plots measured at different dc bias voltages are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. The Z\u0026prime;-axis represents the real part of impedance associated with the shunt/recombination resistance, while the Z\u0026Prime;-axis corresponds to the imaginary part is related to the capacitive reactance arising from the junction/trap capacitance [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, all impedance spectra exhibit a semi-circular arc, which is characteristic of a system that could be modelled by a resistor-capacitor (RC) equivalent circuit. This confirms that the MOS structure exhibits both resistive and capacitive behaviour. The frequency dependent impedance of the MOS structure is represented as,\u003cdiv id=\"Equ6\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ6\" name=\"EquationSource\"\u003e\n$$\\:Z\\:\\left(\\omega\\:\\right)={Z}^{{\\prime\\:}}\\left(w\\right)+j{Z}^{{\\prime\\:}{\\prime\\:}}\\left(\\omega\\:\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e7\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cem\u003eω\u003c/em\u003e is the angular frequency, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{Z}^{{\\prime\\:}}\\)\u003c/span\u003e\u003c/span\u003eand \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{Z}^{{\\prime\\:}{\\prime\\:}}\\)\u003c/span\u003e\u003c/span\u003e denotes the real and imaginary components of the impedance respectively.\u003cdiv id=\"Equ7\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ7\" name=\"EquationSource\"\u003e\n$$\\:{Z}^{{\\prime\\:}}=\\frac{{R}_{ox}}{1+{\\left(\\omega\\:{R}_{ox}{C}_{ox}\\right)}^{2}}+\\frac{{R}_{X}}{1+{\\left(\\omega\\:{R}_{X}{C}_{X}\\right)}^{2}}+{R}_{s}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e8\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ8\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ8\" name=\"EquationSource\"\u003e\n$$\\:{Z}^{{\\prime\\:}{\\prime\\:}}=-\\frac{\\omega\\:{R}_{ox}^{2}{C}_{ox}}{1+{\\left(\\omega\\:{R}_{ox}{C}_{ox}\\right)}^{2}}-\\frac{\\omega\\:{R}_{X}^{2}{C}_{X}}{1+{\\left(\\omega\\:{R}_{X}{C}_{X}\\right)}^{2}}+\\omega\\:L$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e9\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe diameter of the semicircle in the Cole\u0026ndash;Cole plot varies with the applied gate voltage, reflecting the corresponding changes in the total impedance of the device. In the inversion regime, as the gate voltage increases from 0.4 V to 1.2 V, the semicircle expands along the real axis (Z\u0026prime;), indicating an increase in shunt (recombination) resistance from ~\u0026thinsp;170 MΩ to 200 MΩ. This is consistent with the widening of depletion region as the reverse bias increases, which reduces the recombination rate by spatially separating the charge carriers. As the gate voltage is further increased to -1.6 V, the shunt resistance decreases to 165 MΩ. This reduction signifies the transition into the deep inversion regime, where the formation of a dense inversion layer dominates the electrical response. The increased density of mobile holes in the inversion layer enhances the conductivity near the surface, thereby lowering the recombination resistance.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eFitting parameters extracted from the impedance spectra shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e using the equivalent RC circuit model depicted in the inset. Here R and C describe the resistance and capacitance, respectively, associated with the HfO\u003csub\u003ex\u003c/sub\u003e/Si interface.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVoltage (V)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eR (MΩ)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC (pF)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e-1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e165.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e165.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e-1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e180.1\u0026thinsp;\u0026plusmn;\u0026thinsp;1.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e164.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e-1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e200.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e161.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e-0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e188.1\u0026thinsp;\u0026plusmn;\u0026thinsp;1.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e165.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e-0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e170.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e169.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eHfO\u003csub\u003ex\u003c/sub\u003e thin films were deposited by PEALD at different plasma powers (\u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e) in order to assess their passivation quality on crystalline silicon. Effective passivation of c-Si surfaces achieved using HfO\u003csub\u003ex\u003c/sub\u003e thin films at an optimum power of 2500 W, followed by an activation anneal at 400\u0026deg; C under nitrogen ambient, which preserved the amorphous nature of HfO\u003csub\u003ex\u003c/sub\u003e films. AFM analysis showed that HfO\u003csub\u003ex\u003c/sub\u003e films were exceptionally smooth with an average roughness below 2 \u0026Aring;. FTIR analysis indicated the formation of an interfacial layer comprising a mixed SiOₓ and HfO\u003csub\u003ex\u003c/sub\u003e phase, resulting from interfacial reactions during film deposition. XPS analysis revealed that increasing deposition power to 2500 W reduced oxygen-related defect states in HfO\u003csub\u003ex\u003c/sub\u003e films. C-V analysis revealed that chemical passivation has been the dominant mechanism contributing to the improved interface quality. This was supported by lower \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e of 3.28 \u0026times; 10\u003csup\u003e12\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e eV\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at the HfO\u003csub\u003ex\u003c/sub\u003e/Si interface, and moderate fixed charge densities, indicating a limited contribution from filed effect passivation. As a result, an SRV less than 45 cm/s was achieved for the film thickness of 16 nm on n-type silicon substrates. The corrected C-V and G-V analyses further highlighted impact of series resistance (\u003cem\u003eRₛ\u003c/em\u003e), which must be accounted for to accurately assess device characteristics. Impedance spectroscopy confirmed the RC behaviour of the MOS structure, with bias-dependent trends revealing changes in recombination resistance across inversion and depletion regimes. The results demonstrate the potential of amorphous HfO\u003csub\u003ex\u003c/sub\u003e films deposited by PEALD as a promising passivation layer for high-efficiency silicon-based electronic and photovoltaic devices.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRinki:\u003c/strong\u003e Writing - original draft, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. \u003cstrong\u003eMeenakshi:\u003c/strong\u003e Formal analysis, Data curation, Conceptualization. \u003cstrong\u003eParas:\u003c/strong\u003e Formal analysis, Investigation. \u003cstrong\u003eAnil:\u003c/strong\u003e Formal analysis, Investigation. \u0026nbsp;\u003cstrong\u003eShivanshu:\u003c/strong\u003e Formal analysis, Investigation. \u003cstrong\u003eUttam Kumar Goutam\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eFormal analysis, Investigation\u003cstrong\u003e\u0026nbsp;Mrinal Dutta:\u003c/strong\u003e Software, Resources, Formal analysis, Investigation. \u003cstrong\u003eSanjay K. Srivastava:\u003c/strong\u003e Formal analysis, Investigation. \u0026nbsp;\u003cstrong\u003eParamita Guha:\u003c/strong\u003e Formal analysis, Investigation\u003cstrong\u003e\u0026nbsp;Prathap Pathi:\u003c/strong\u003e Writing-review \u0026amp; editing, Supervision, Formal analysis, Conceptualization, Resources, Methodology, Investigation, Funding acquisition.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026ensp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this article.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest\u003c/strong\u003e\u0026emsp;The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors are thankful to CSIR-National Physical Laboratory, New Delhi, for providing the research facilities, Council of Scientific and Industrial Research (CSIR), for fellowship support (Grant No. 31/0001(15737)/2022-EMR-I). This work is partly supported by the project (Ref. No. CPRI/R\u0026amp;D/TC/GDEC/2024) sponsored by MNRE, Govt. of India.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eGope, J., Batra, N., Panigrahi, J., Singh, R., Maurya, K. K., Srivastava, R., \u0026amp; Singh, P. K. (2015). Silicon surface passivation using thin HfO2 films by atomic layer deposition. Applied Surface Science, 357, 635-642.\u003c/li\u003e\n\u003cli\u003eMuduli, S. P., \u0026amp; Kale, P. (2023). State-of-the-art passivation strategies of c-Si for photovoltaic applications: A review. \u003cem\u003eMaterials Science in Semiconductor Processing\u003c/em\u003e, \u003cem\u003e154\u003c/em\u003e, 107202.\u003c/li\u003e\n\u003cli\u003eAber, A. G., Glunz, S., \u0026amp; Warta, W. (1993). 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MOS (Metal Oxide Semiconductor) Physics and Technology (Wiley-Interscience: John Wiley \u0026amp; Sons, New York. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Surface passivation, PEALD, HfOₓ, Impedance spectroscopy ","lastPublishedDoi":"10.21203/rs.3.rs-8590256/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8590256/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the silicon surface passivation characteristics of hafnium oxide (HfOₓ) thin films deposited using plasma-enhanced atomic layer deposition (PEALD), with a particular focus on remote plasma power (\u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e) induced growth mechanism of the films. The HfOₓ films were grown on Si (100) wafers at a substrate temperature of 200\u0026deg;C using tetrakis(ethyl-methyl-amino)hafnium (TEMAHf) as the metal precursor and oxygen plasma as the oxidant. Structural analysis performed using grazing incidence X-ray diffraction (GIXRD) confirmed the amorphous nature of all the films, while atomic force microscopy (AFM) revealed smooth surfaces with roughness\u0026thinsp;\u0026lt;\u0026thinsp;0.2 nm. The variation of films thickness, as evaluated using, spectroscopic ellipsometry showed that growth per cycle (GPC) varied with plasma power. XPS analysis revealed that plasma power of 2500 W effectively suppressed oxygen-related defect states in the HfOₓ films. A maximum effective minority carrier lifetime (\u003cem\u003eτ\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e) of 390 \u0026micro;s, corresponding to a surface recombination velocity (SRV)\u0026thinsp;\u0026lt;\u0026thinsp;50 cm/s was achieved for the films with a thickness of 16 nm, deposited at a \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e of 2500 W. Plasma induced modifications on silicon surface were studied using electrical characterization of its MOS capacitors and the results indicate that chemical passivation at the Si/HfOₓ interface played a dominant role in reducing the interface trap density (\u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eit\u003c/em\u003e\u003c/sub\u003e). These results emphasise the critical role of plasma power in optimizing the growth dynamics and passivation performance of PEALD-grown HfOₓ films for advanced silicon-based devices.\u003c/p\u003e","manuscriptTitle":"Plasma-Enhanced ALD of HfOx for Effective Surface Passivation of Silicon: A Material and Interface Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-22 11:12:55","doi":"10.21203/rs.3.rs-8590256/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"23a3bd93-4478-4588-a9f2-2075efb25a06","owner":[],"postedDate":"January 22nd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-22T11:12:55+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-22 11:12:55","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8590256","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8590256","identity":"rs-8590256","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}