Morphological and Electrical Features of Porous Silicon Prepared by Metal-Induced Chemical Etching

Morphological and Electrical Features of Porous Silicon Prepared by Metal-Induced Chemical Etching | 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 Morphological and Electrical Features of Porous Silicon Prepared by Metal-Induced Chemical Etching Hyo Han Kim, Sang Ho Lee, Hyun Soon Park This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4380378/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 27 Sep, 2024 Read the published version in Silicon → Version 1 posted 10 You are reading this latest preprint version Abstract Porous silicon (PS) was produced by the metal-induced chemical etching of p-type Si wafers. Patterned platinum dots (~ 300 µm) were deposited on a Si wafer by DC magnetron sputtering for 15 s. When the H 2 O 2 fraction in the etchants consisting of HF and H 2 O 2 was increased from 0.3 to 24%, the etching behavior changed from “pore formation” to “electropolishing.” The etching reaction activation energy also changed from 0.20 to 0.36 eV in the ln J–K(current–etchant temperature) relationships. The etched morphologies exhibited different structures, such as nano-scaled sponge-like and 3D micro-scaled pore structures, according to the H 2 O 2 ratio. The etched layers contained a Si quantum structure, amorphous Si phase, and SiO x . These phase ratios changed according to the etching behavior. The Si nanocrystallite size changed from ~ 3.0 to 4.6 nm, emitting optical features in the band gap range of 1.73 to 1.88 eV. The fluorescence region varied according to the H 2 O 2 ratio. The fluorescence preferentially occurred at the interface between the metal circle and Si wafer in the case of etched PS by an etchant containing a lower hydrogen peroxide ratio. In contrast, the fluorescence increased in the non-coated region from 19.5 to 24.0%. Metal-induced chemical etching Porous silicon Etching behavior Anodization Optical properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Canham LT, Cullis AG and others reported that a quantum confinement effect occurred when Si nanocrystallites smaller than 5 nm were formed in porous silicon produced by electrochemical anodization. This effect caused a change from an indirect band structure to a pseudo-direct band structure, and the photoluminescence phenomenon occurred due to a quantum confinement effect. [ 1 , 2 ] The band gap changes according to the Si nanocrystallite size within an etching structure. When numerous atoms exist in the same K-space, their energy levels will overlap. On the other hand, these energy levels cannot overlap simultaneously due to Pauli’s exclusion principle, leading to separation into the conduction and valence bands. In the case of silicon, the separated energy band gap is approximately 1.12 eV. Spatial constraints reduce the overlapping energy levels when the Si nanocrystallite size is smaller than 5nm, thinning the energy band and increasing the band gap. In addition, when the Si nanocrystallite size is decreased below the radius of an exciton, the energy levels that electrons and holes can occupy within the valence and conduction bands become greater than those at the band edge. Therefore, the degree of reduction in energy levels changes with the Si nanocrystallite size, and the band gap also changes [ 3 ]. For this reason, nanocrystalline silicon with quantum structures has attracted considerable interest. Si nanocrystallites are generally manufactured using electrochemical etching and thin film deposition. These two methods show variations in the principles of quantum structure formation, resulting in differences in the optical and electrical features. Hence, extensive research has been conducted on the application area and mechanism identification [ 4 – 8 ]. In particular, the quantum structures formed in porous silicon manufactured by electrochemical etching exhibit strong luminescence at room temperature. Significant changes in morphological, optical, and electrical features are observed depending on the etching conditions, such as electrolyte characteristics and secondary treatments, leading to extensive research since the 1990s [ 6 , 7 ]. Accordingly, porous silicon has been used in gas sensors, biosensors, and other applications owing to its excellent optical features. In addition, there are reports that it is also used as an anode material in lithium-ion batteries because of physical advantages such as a broader surface and excellent ion storage amount compared to graphite [ 8 – 14 ]. The most commonly used methods for producing porous silicon include chemical methods, such as electrochemical etching in electrolyte solutions, and physical methods using large etching equipment, e.g., reactive ion etching (RIE) in vacuum environments [ 15 – 17 ]. Among them, electrochemical etching has been studied extensively because it allows the easy fabrication of porous silicon and offers advantages in process time and cost compared to other physical methods. This electrochemical etching technique includes directly applying a current in an electrolyte and etching using a self-electric potential generated through metal catalysts. When a noble inert metal (e.g., Pt, Au, and Ag) comes into contact with a Si wafer, the flow of electrons and holes occurs due to a difference in work function. The interface is in the thermal equilibrium state, and electrochemical etching is carried out using the self-potential generated in this process [ 18 – 20 ]. Thus far, many studies have suggested that metal catalyst etching (MICE) induces macroscopic changes in the etched morphologies depending on the composition and temperature of the etching solution and the type of catalyst metal [ 18 , 19 , 21 ]. Such changes in etched morphologies will be accompanied by changes in the physical and optical characteristics. Hence, structural changes must precede to induce various characteristic changes in porous silicon. This is closely related to the etching behavior. The hole is the majority carrier in p-type Si, and the etching behavior changes according to the behavior of the holes because the etching reaction originates from the recombination of holes and electrons. Therefore, the structural and optical characteristics of porous silicon vary with the etching behavior [ 6 , 22 ]. Nevertheless, the studies presented thus far on the electrochemical etching technique using metal catalysts focused on the application of devices based on porous silicon. Moreover, detailed studies are needed on the correlation between various characteristics of porous silicon manufactured by metal-induced chemical etching. This study examined the correlation between the morphological, electrical, and optical features of porous silicon prepared by MICE. 2. Experimental procedure The porous silicon was fabricated using a metal catalyst, and a p-type Si wafer with a resistivity of 0.005 Ω•cm was applied. Before MICE, piranha and HF cleaning were carried out to remove the organic contamination and native oxide layer. Platinum was used as a metal catalyst. A 300 µm-patterned metal catalyst was deposited approximately 5–6nm thick by DC magnetron sputtering for 15. In this study, the p-type Si wafer has a work function of approximately 5.08 eV and a doping concentration of 2.05 × 10 19 atoms/cm 3 . The work function of the platinum used as the catalyst was 5.93 eV [ 23 ]. Band bending occurs when these materials are in contact with each other. The difference between the Fermi energy and the highest state of the valence band was calculated to be 0.02 eV using Eq. 1. Figure 1 presents the band structure of contact between platinum and p-Si. This contact shows ideal ohmic contact in which the carrier flow occurs easily at a low electric potential. Therefore, the depletion layer will be minimal or not occur at all [ 24 ]. The electrolytes included HF (49% diluted), DIW (deionized water), and hydrogen peroxide (H 2 O 2 -30% diluted). The H 2 O 2 content in the electrolytes was varied from 0.3 to 24.0%. Table 1 lists the composition of each component in the solution. Table 1 Composition of the electrolytes # of Samples and electrolytes H 2 O 2 ratio HF ratio DIW ratio 1 0.30% 48.51% 51.19% 2 3.00% 44.10% 52.90% 3 5.10% 40.67% 54.23% 4 9.90% 34.30% 55.80% 5 15.00% 24.50% 60.50% 6 19.50% 17.15% 63.35% 7 22.50% 12.25% 65.25% 8 24.00% 9.80% 66.20% MICE was carried out for 20 min without an electrical potential, and a current flowed spontaneously by the carrier behavior during MICE. This electrical potential was measured using a source meter (Keithley, 2425). The changes in the etched structure were observed by field-emission scanning electron microscopy (FESEM, Hitachi S-4300). Raman spectroscopy (Horiba Jobin Yvon LabRam HR) was conducted to examine the nanostructural characteristics. The optical features were analyzed using a spectrofluorophotometer (Dongwoo Optron RAM Boss) and confocal laser microscopy (Zeiss LSM 510 META). \({\varvec{\rho }}_{0}={\varvec{N}}_{\varvec{V}}\varvec{e}\varvec{x}\varvec{p}\left[\frac{-({\varvec{E}}_{\varvec{F}}-{\varvec{E}}_{\varvec{V}})}{\varvec{K}\varvec{T}}\right]\) Eq. (1) 3. Results and Discussion 3.1. Morphological features Figure 2 shows surface and cross-sectional SEM images of porous silicon etched for 20 minutes at various H 2 O 2 concentrations. The etching morphologies changed according to the H 2 O 2 content (б). In the case of samples 2 and 3, the cross-section of the porous silicon exhibited a ‘sponge-like’ structure, with pores several hundred nanometers in size. In the case of the etched surface, the etching reaction occurred uniformly within the Pt-deposited areas. When the б was 22.5% (sample 7), the ‘sponge-like’ structure disappeared, and micrometer-scale pores formed on the etched surface. This etching structure formed preferentially from the center region of the etched surface. The density of the etched structure tended to increase in outer regions, and the etched structure size decreased gradually. As shown in Fig. 3 , inhomogeneous etching also occurred at the non-coated region between two metal discs in the case of sample 7. These results suggest that changes in the distribution and amount of applied electrical potential occurred depending on the composition of the electrolytes. In the case of sample 8, a pseudo ‘sponge-like’ structure formed again at the cross-section. Nanometer-scaled pores were observed at the inside of the etched structure, and the density of the etched structure decreased. When the б was increased, the rate of hole consumption was lower than its generation rate at the metal-deposited region. Consequently, the number of excess holes increases, and they diffuse from the etch tips to the outer region of the pore or non-coat region [ 18 ]. In addition, when the H 2 O 2 concentration is high, the mobility of holes decreases, leading to the diffusion of excess holes that do not reach the metal deposition area across the surface of the silicon wafer. As a result, random etching occurs on the silicon surface. Hence, the distribution and magnitude of the applied electric potential change according to the etching site. These phenomena are caused by the stronger hydrogen bonds between H 2 O 2 molecules than those in water molecules. Therefore, as ‘б’ increases, the hydrogen bonds increase, and the bonding between the molecules in the liquid state will be stronger, increasing internal friction [ 25 ]. An inhomogeneous distribution of etch rates occurred in the metal deposited area when the б was increased because of decreasing hole mobility. Inhomogeneous etching also occurred in non-coated areas. From the cross-sectional images of porous silicon, the vertically formed sponge structures gradually disappeared when б increased. According to Chartier et al., when the б is increased, holes are consumed on the outer walls of the etching pores, and the overall pore size will increase [ 26 ]. As б increases, even using the same metal, the increased generation of holes results in a relatively stronger electric potential. These phenomena will cause “electropolishing,” where micropores rather than nanopores are formed. From this point, the thickness of the formed SiO x layer increases, and the etching rate will be lower [ 22 ]. Furthermore, saturated holes that fail to reach the deposition area diffuse into areas where the metal is not coated, causing etching even in the uncoated areas. On the other hand, the etching rate in these non-coated areas is lower than in the metal-coated areas. This has been attributed to a depletion layer between the silicon and the etching solution in the non-coated regions. Hence, the supplying pattern of holes is also changed when the H 2 O 2 concentration is changed. These phenomena will cause changes in the etching behavior of porous silicon. 3.2 Electrical Features Table 2 Electrical properties of the porous silicon prepared by metal-induced chemical etching Etchant temp.(K) 290 / 310 # of sample and electrolytes 1 2 3 4 5 6 7 8 H 2 O 2 ratio(б) (%) 0.3 3.0 5.1 9.9 15.0 19.5 22.5 24.0 Current Density (A/m 2 ) 293 / 493 658 / 1173 667 / 1289 444 / 978 378 / 933 178 / 413 129 / 293 89 / 202 ln J 5.68 / 6.20 6.49 / 7.07 6.50 / 7.16 6.10 / 6.89 5.93 / 6.84 5.18 / 6.02 4.86 / 5.68 4.49 / 5.31 Y-intercept 13.72 15.48 16.86 17.70 20.30 18.50 17.84 17.49 Slope /1000 −2.34 −2.61 −3.00 −3.64 −4.15 −3.85 −3.76 −3.76 E a (290→310K) (eV) 0.20 0.23 0.26 0.31 0.36 0.33 0.32 0.32 As ‘б’ increased, the activation energy increased from 0.20 eV to 0.36 eV. In the case of sample 5, the activation energy was maximum, and the activation energy decreased from this concentration. When the etching behavior was ‘pore formation,’ the behavior of holes supplied from H 2 O 2 was confined to the platinum deposition area. Furthermore, SEM showed that this resulted in a vertical ‘sponge-like’ etching structure. Moreover, as the first step of the etching procedure, etching occurs only in a limited area. Therefore, the activation energy required for etching is expected to be lower. As the H 2 O 2 concentration increased, the number of holes increased, and etching occurred even in the non-coated region, as shown by the SEM results. These results suggest an increase in activation energy [ 18 ]. The increase in activation energy is associated with changes in etching behavior. As shown in previous SEM results, when ‘б’ was changed from 5.1–22.5%, the etching structure within the platinum deposition area transformed from a vertical nanoscale to a 3D microscale. These changes showed that the etching behavior was changed from “pore formation” to “electropolishing.” During the etching process, the main reactions, such as the dissolution of silicon and the formation of SiO x layers, occur selectively depending on whether an overpotential occurs on the surface. This selective variation changes the reaction activation energy [ 22 ], which is related to the behavior of holes. The etching rate in the ‘pore formation’ stage is determined by the Si dissolution occurring at the interface between the Si and the deposited metal. Moreover, in the “electropolishing” stage, the etch rate is determined dominantly by the formation and dissolution of the Si oxide film. In addition, the reaction activation energy is influenced by the overpotential within the reaction system and the diffusion of holes in the uncoated area. In electrolytes with relatively lower HF concentrations, the dissolution reaction of the anodic oxide film was not rapid. Therefore, as the H 2 O 2 content increased, the SiO x film remained even after the reaction in the etching behavior of “electropolishing” [ 28 ]. Such changes in surface characteristics caused variations in the optical properties based on the quantum structure. When ‘б’ > 15%, although the absolute value of the current density decreases, the activation energy value was saturated above 0.3 eV. These phenomena mean the etching behavior persists in the “electropolishing” stage. As an oxide layer gradually accumulated on the surface during etching, it acted as an insulator, causing a potential drop and interfering with charge transfer. In the state where micrometer-scale etching structures formed, the reaction induced by randomly over-supplied holes led to the spread of defects acting as etching tips up to the uncoated areas. Consequently, the etching reaction of three-dimensional micrometer-scale structures will persist across the entire area exposed to the electrolyte [ 22 ]. The possibility of macropore formation increases when the conductivity of the electrolyte solution is lower than that of the Si wafer. If the doping concentration of Si is reduced, “electropolishing” behavior will occur at even lower ‘б’ than observed in the present results. As etching progressed gradually, the Si wafer with a resistivity of 0.005 Ω•cm changed from semi-metallic to more insulating. Therefore, the formation of macropores occurred. Table 1 lists the activation energy calculated from the measured electrical potential and detailed results. The slope represents the etch rate, and the Y-intercept signifies the potential barrier [ 29 , 30 ]. As ‘б’ increased, the etch rate also increased under the same conditions. The contact between highly doped p-type Si and platinum exhibited ideal ohmic contact. Hence, there is a very thin potential barrier at the interface. As the temperature or ‘б’ increases, more carriers can overcome the potential barrier, enhancing the tunneling phenomena. Therefore, even if the barrier increases, rapid changes in the etching behavior and increasing phenomena of etch rate were observed for the same process time. 3.3 Nanostructural features Figure 5 shows the Raman spectroscopy results of porous silicon according to the H 2 O 2 ratio (б). The peaks were deconvoluted by Gaussian function to each of the spectra. The symmetric peak of bulk Si occurred dominantly at 521 cm − 1 . Furthermore, the broad peak at 480 cm − 1 represents the Transverse Optical (T.O) vibrations of the Si amorphous phase, while the region from 490 to 520 cm − 1 corresponds to Si nanocrystallites[ 31 – 33 ]. In addition, the various peaks were separated by Si vibrational movements. Among the several peaks, the SiO x peak was observed in the 430 cm − 1 region [ 34 ]. Figure 5 d shows the calculated fractions for the three components (Si nanocrystals, amorphous areas, and SiO x ), excluding the dominant bulk Si peak among the separated peaks in each region. Furthermore, the size of the Si nanocrystallite was calculated using Eq. 3 [ 33 ]. \(\text{D}=2{\pi }\sqrt{\frac{B}{\varDelta \omega }}\) Eq. (3) where ∆w is the shifting value in the Si nanocrystallite peak from the bulk silicon (521 cm − 1 ), and B is the full-width at half-maximum (FWHM) of bulk silicon, which is 2.0 cm − 1 nm 2 in this study. When б was varied from 3.0 to 24.0%, the size of the nc-Si changed from 3.0 to 4.6 nm, respectively. On the other side, the Si bulk peak only occurred in the case of sample 1. A sufficient etching reaction did not occur to form a Si quantum structure. Moreover, among the various separated peaks, the fraction of peaks related to the quantum structure, which includes the Si nanocrystallite, changed from 57 to 38.5% when б was varied. Although the changes were not continuous and uniform because the measurement was carried out in only a part of the entire region, there was a tendency for the fraction of the quantum structure to decrease when the б was increased. Furthermore, the volume fraction of SiO 2 was highest at 44.8% in the case of sample 4, and it gradually maintained again to approximately 24–30% when the б > 15.0%. The volume fraction of the amorphous phase was also maintained around 28% in the б range. These results suggest that when the б > 9.9%, the etching behavior was maintained as “electropolishing,” and SiO 2 formation occurred preferentially over nc-Si formation in this б range. Table 3 provides detailed results. These phenomena induced the transitions in the emission region or variations in emission intensity of the luminescence phenomenon based on the nanocrystals. Table 3 Detailed data of the nanostructural features of the porous Si prepared by metal-induced chemical etching Sample Etchant # 2 3 4 5 6 7 8 H 2 O 2 ratio (б) (%) 3.0 5.1 9.9 15.0 19.5 22.5 24.0 nc-Si (nm) 3.0 3.3 3.4 3.5 3.8 4.4 4.6 Amorphous phase (%) 25.3 22.2 14.9 28.0 28.6 25.7 28.7 Quantum structure (%) 57.0 55.6 40.3 48.0 46.6 48.7 38.5 SiO 2 (%) 17.7 22.2 44.8 24.0 24.8 25.6 30.8 3.4 Optical features Figure 6 presents the photoluminescence (PL) spectra of the MICE-prepared porous silicon. The maximum peaks were observed from 661 to 716nm when б was increased from 3.0 to 24.0%. These wavelengths corresponded to band gaps of 1.88 to 1.73 eV. In the case of sample 1, photoluminescence did not occur due to the insufficient existence of quantum structures referring to the Raman spectroscopy results. The PL intensity decreased gradually as б was increased. Hence, the etching behavior changes according to “δ.” The fraction of amorphous phase and SiO 2 increased when the etching behavior was ‘electropolishing,’ while the fraction of silicon nanocrystals decreased, causing a decrease in PL intensity. Furthermore, the transition of etching behavior to electropolishing, leading to the coarsening of the etching structure, is also a cause of the decay of quantum structures. In the case of sample 3, the PL intensity was highest. According to the Raman spectra, this was associated with the second-largest volume fraction of the peak in the vibration of the quantum structure, which was 55.6%. In the case of sample 2, the quantum structure ratio was higher than that of sample 3. but the PL intensity observed in both cases is similar because the fraction of the amorphous phase is also high. On the other hand, in the case of sample 8, which exhibited the weakest PL intensity, the volume fraction of the peak in the vibration of the Si quantum structure ratio was lowest at 38.5%. This is related to the etching behavior. The formation of quantum structures contributing to luminescence is closely related to the etched morphologies. The mobility and behavior of holes also changed when the etching behavior was varied. Consequently, the etching morphologies changed with ‘б,’ as observed by SEM. In addition, the quantum structures contributing to the PL phenomena were generally located at the etched surface. Hence, the positions of the quantum structure were selectively different with etched morphologies. When the etching behavior is “electropolishing,” vertical etching occurs as the etching process progresses, and the deposition metal, which serves to supply holes from H 2 O 2 , moves to a lower position. Consequently, the quantum structures formed by the anodic oxidation reaction exist at lower positions as the reaction proceeds [ 35 ]. These phenomena interfere with the direct contribution of nanocrystals to photoluminescence, leading to a decrease in PL intensity. Table 4 lists the detailed results. Table 4 Detailed results of the optical features of the porous Si prepared by metal-induced chemical etching Sample Etchant # 2 3 4 5 6 7 8 H 2 O 2 ratio (б) (%) 3.0 5.1 9.9 15.0 19.5 22.5 24.0 nc-Si size (nm) 3.0 3.3 3.4 3.5 3.8 4.4 4.6 Band gap (eV) 1.84 1.77 1.88 1.81 1.77 1.76 1.73 Max. PL intensity (nm) 238 251 247 239 231 232 227 Amorphous phase (%) 25.3 22.2 14.9 28.0 28.6 25.7 28.7 Quantum structure (%) 57.0 55.6 40.3 48.0 46.6 48.7 38.5 Figure 7 shows confocal laser microscopy images of porous silicon samples etched in solutions with varying H 2 O 2 concentrations. In the case of sample 1, fluorescence characteristics were observed only in the regions where the interface between coated metal and Si substrate. As the H 2 O 2 concentration increased, the area exhibiting fluorescence characteristics expanded gradually, starting from the platinum-silicon wafer interface. In the case of sample 5, the fluorescence characteristics appeared throughout the entire deposited area. In the case of sample 6, the fluorescence characteristics were observed in the metal-deposited areas and other parts. This is because the behavior of electrons and holes changes with the H 2 O 2 concentration. The supply of holes increases as б increases, leading to a surplus of holes over the amount needed for the etching reaction at the metal-silicon interface. Therefore, the excess holes diffuse into the non-coated areas of the silicon wafer, where they generate additional electric potential, causing etching and generating random quantum structures on the surface. Consequently, fluorescence characteristics appear even outside the metal-deposited region [ 18 ]. When the H 2 O 2 concentration was 24.0%, most areas exhibited fluorescence characteristics. These observations were attributed to the variation in etching behavior and changes in the distribution of nanostructures due to the varying H 2 O 2 concentration. 4. Conclusions Porous silicon prepared by MICE according to the H 2 O 2 content showed a change in the activation energy depending on the etching behavior. As the H 2 O 2 content increased, the etching behavior changed from “pore formation” to “electropolishing,” leading to a change in the etching morphologies. When the etching behavior changed, the etching morphologies varied from a ‘sponge-like’ structure to the 3D micro-pores. Furthermore, when the H 2 O 2 concentration exceeded 19.5%, the etching reaction occurred in the platinum deposition area and non-coated areas. This result was attributed to the change in the supplying behavior of holes throughout the entire surface as the H 2 O 2 concentration increased, leading to diffusion into the non-coated areas. The activation energy also changed according to the etching behavior. The reaction activation energy changed from 0.2 to 0.36 eV when the etching behavior shifted from “pore formation” to “electropolishing.” The activation energy was saturated at approximately 0.3 eV when the H 2 O 2 concentration was 15.0%, and the etching structure appeared in the mixed form of sponge and three-dimensional micro-pores when the H 2 O 2 concentration was increased further. When the etching behavior was changed, the Raman vibration related to the SiO x and Si amorphous phase in the overall phase was increased. When the H 2 O 2 ratio was increased, the PL characteristics in the wavelength range changed from 661 nm to 716 nm, and the size of the nanocrystals decreased from 4.6 nm to 3.0 nm. The luminescence intensity decreased as the H 2 O 2 ratio increased. Hence, the quantum structure contributing to the emission was gradually positioned at the lower etched region as the etching behavior changed. Furthermore, as etching progresses, the increase in volume fraction of the Si amorphous and SiO x phases was also considered to influence the decrease in PL intensity. The fluorescence characteristics on the etched surface varied as the H 2 O 2 ratio increased. The fluorescence characteristics that occurred primarily at the interface between silicon and platinum spread throughout the platinum-coated area and even to the non-coated areas as the H 2 O 2 concentration increased. The nanostructural and optical features of porous silicon prepared by MICE were dependent on the variations in the H 2 O 2 ratio. Declarations The authors of this work confirm that the results of this study do not involve humans or animals in this work. Ethics Approval Not Applicable Consent to Participate Not applicable Consent to Publication Corresponding author Professor Hyun Soon Park grants permission to publish this manuscript in the journal ‘Silicon’ if it is accepted. Availability of data and materials The datasets used and / or analyzed during the current study available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests. Funding This research was supported by an Inha University Research Grant (INHA-67987). Author Contribution Hyo Han Kim is a Ph.D candidate under Professor Hyun Soon Park and a researcher at ULVAC, where he conducted experiments, analyses, and drafted the manuscript. Sang ho Lee is Hyo Han Kim's manager at ULVAC and reviewed the draft together with Professor Park HS. Professor Hyun Soon Park is Hyo Han Kim's advisor, provided funding support for the research, and reviewed and revised the manuscript draft. 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Cite Share Download PDF Status: Published Journal Publication published 27 Sep, 2024 Read the published version in Silicon → Version 1 posted Editorial decision: Revision requested 06 Aug, 2024 Reviews received at journal 17 Jul, 2024 Reviews received at journal 15 Jul, 2024 Reviewers agreed at journal 12 Jul, 2024 Reviewers agreed at journal 11 Jul, 2024 Reviewers agreed at journal 16 Jun, 2024 Reviewers invited by journal 30 May, 2024 Submission checks completed at journal 21 May, 2024 Editor assigned by journal 21 May, 2024 First submitted to journal 07 May, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4380378","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":309420063,"identity":"91a3953d-08b8-4408-b972-5eaca007392d","order_by":0,"name":"Hyo Han Kim","email":"","orcid":"","institution":"Inha University","correspondingAuthor":false,"prefix":"","firstName":"Hyo","middleName":"Han","lastName":"Kim","suffix":""},{"id":309420064,"identity":"62fcf05e-206e-4fb0-b370-b87bcf2ef979","order_by":1,"name":"Sang Ho Lee","email":"","orcid":"","institution":"ULVAC Korea, ATI K","correspondingAuthor":false,"prefix":"","firstName":"Sang","middleName":"Ho","lastName":"Lee","suffix":""},{"id":309420065,"identity":"42bfe05e-c1a7-4d07-a20d-3cd50c4ceb56","order_by":2,"name":"Hyun Soon Park","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIie3OsQrCMBCA4ZOALpWu7VJfoSKoXXwWS8FJC+IiCBoQ6uID6Ft0dIwE7HLiGjdBcHJQnNw8uxaibg75h3A3fOQATKY/zM9f4dDAhCjxfGXfknL3J/IeLB++Ii17v32MsR23KniXw00H7IVgjbGGBKs4clE5o2A5SOUaI3Cwy0LUHaYs3+U3J0wFkWpCNylgW64jB2w8c3K4nojMoPaRiH7T5YqI6gMRSf8CC7VExb2A45tcfCKZVcdwXtcftpdHvpvSYdH5UU0mnpdJ6eoIgFVYS3pQICaTyWQq9AJtvVXsZNT+RQAAAABJRU5ErkJggg==","orcid":"","institution":"Inha University","correspondingAuthor":true,"prefix":"","firstName":"Hyun","middleName":"Soon","lastName":"Park","suffix":""}],"badges":[],"createdAt":"2024-05-07 05:31:39","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4380378/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4380378/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s12633-024-03151-0","type":"published","date":"2024-09-27T15:57:33+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":57937856,"identity":"86d870df-7721-4bf3-8ba7-168822bf4f9f","added_by":"auto","created_at":"2024-06-07 17:43:58","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":82808,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the band structure of platinum-p-type Si wafer contact, which is applied to this experiment. Images (a) and (b) show before and after contact between platinum and p-type silicon wafers, respectively\u003c/p\u003e","description":"","filename":"Fig.1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4380378/v1/711ee5b27b8aa8679c4ac5d2.jpg"},{"id":57938195,"identity":"f25fcde7-8a30-4f75-86bb-40d390d0ee83","added_by":"auto","created_at":"2024-06-07 17:51:59","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":254605,"visible":true,"origin":"","legend":"\u003cp\u003eMagnified surface and cross-section images of porous silicon prepared by MICE. Images (a), (b), (c), and (d) were obtained from samples 2, 3, 7, and 8. Each of the magnified surface (Orange marked) and cross-section images (Yellow marked) of porous silicon was inset into the micrographs.\u003c/p\u003e","description":"","filename":"Fig.2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4380378/v1/4101bb4577fb3b8d1e287cdc.jpg"},{"id":57937857,"identity":"d5be6ddd-2152-40ba-b997-d542f79b6a99","added_by":"auto","created_at":"2024-06-07 17:43:58","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":274563,"visible":true,"origin":"","legend":"\u003cp\u003eLow-magnification surface images of porous silicon prepared by MICE. Images (a) and (b) were obtained from samples 2 and 7.\u003c/p\u003e","description":"","filename":"Fig.3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4380378/v1/0710d9d520852b9dda43295a.jpg"},{"id":57937860,"identity":"2b321fed-d0d8-43d9-9056-2870779f57ef","added_by":"auto","created_at":"2024-06-07 17:43:59","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":221307,"visible":true,"origin":"","legend":"\u003cp\u003eMeasured current from porous Si according to the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio (a). (b) is ln J vs temperature. (c) The activation energies required for the etching reaction in terms of the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratios.\u003c/p\u003e","description":"","filename":"Fig.4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4380378/v1/7da901e3b1657f9b31641be8.jpg"},{"id":57937858,"identity":"3d126e90-a7b8-4680-82ed-3b17ff1bbced","added_by":"auto","created_at":"2024-06-07 17:43:59","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":67514,"visible":true,"origin":"","legend":"\u003cp\u003eRaman spectra of porous Si. Raman spectra (a), (b), and (c) were obtained from the samples etched in the etchant with H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentrations of 3.0, 15.0, and 24%, respectively. Graph (d) shows details of the amorphous phase ratio, quantum structure, and SiO\u003csub\u003ex\u003c/sub\u003e according to the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration\u003c/p\u003e","description":"","filename":"Fig.5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4380378/v1/443bae3ae2cd765862beac92.jpg"},{"id":57937861,"identity":"30c7e748-cadf-4a6c-9b32-ad26bb9be696","added_by":"auto","created_at":"2024-06-07 17:43:59","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":474041,"visible":true,"origin":"","legend":"\u003cp\u003ePL spectra of PS prepared by MICE. PL spectra (a) were obtained from samples etched in the etchant with the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio. Graph (b) shows the relationship between the amorphous phase ratio and PL intensity according to the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration.\u003c/p\u003e","description":"","filename":"Fig.6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4380378/v1/ec25c0b63995005843126cf2.jpg"},{"id":57937855,"identity":"5cb7c6df-c314-4680-9ecf-e8dafff1777f","added_by":"auto","created_at":"2024-06-07 17:43:58","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":766753,"visible":true,"origin":"","legend":"\u003cp\u003eConfocal laser microscopy images of the PS samples. Images (a), (b), (c), (d), (e), and (f) were obtained from samples etched in an etchant with H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratios (б) of 5.1, 9.9, 15.0, 19.5, 22.5, and 24.0 %.\u003c/p\u003e","description":"","filename":"Fig.7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4380378/v1/220ea760e395b36c0610303c.jpg"},{"id":65627224,"identity":"f40c4008-26ce-4d35-8588-1cec05fb00ea","added_by":"auto","created_at":"2024-09-30 16:13:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2749759,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4380378/v1/65be1b2f-eb3a-477b-be8d-d105b53aeef4.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Morphological and Electrical Features of Porous Silicon Prepared by Metal-Induced Chemical Etching","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCanham LT, Cullis AG and others reported that a quantum confinement effect occurred when Si nanocrystallites smaller than 5 nm were formed in porous silicon produced by electrochemical anodization. This effect caused a change from an indirect band structure to a pseudo-direct band structure, and the photoluminescence phenomenon occurred due to a quantum confinement effect. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eThe band gap changes according to the Si nanocrystallite size within an etching structure. When numerous atoms exist in the same K-space, their energy levels will overlap. On the other hand, these energy levels cannot overlap simultaneously due to Pauli\u0026rsquo;s exclusion principle, leading to separation into the conduction and valence bands. In the case of silicon, the separated energy band gap is approximately 1.12 eV. Spatial constraints reduce the overlapping energy levels when the Si nanocrystallite size is smaller than 5nm, thinning the energy band and increasing the band gap. In addition, when the Si nanocrystallite size is decreased below the radius of an exciton, the energy levels that electrons and holes can occupy within the valence and conduction bands become greater than those at the band edge. Therefore, the degree of reduction in energy levels changes with the Si nanocrystallite size, and the band gap also changes [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFor this reason, nanocrystalline silicon with quantum structures has attracted considerable interest. Si nanocrystallites are generally manufactured using electrochemical etching and thin film deposition. These two methods show variations in the principles of quantum structure formation, resulting in differences in the optical and electrical features. Hence, extensive research has been conducted on the application area and mechanism identification [\u003cspan additionalcitationids=\"CR5 CR6 CR7\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In particular, the quantum structures formed in porous silicon manufactured by electrochemical etching exhibit strong luminescence at room temperature. Significant changes in morphological, optical, and electrical features are observed depending on the etching conditions, such as electrolyte characteristics and secondary treatments, leading to extensive research since the 1990s [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Accordingly, porous silicon has been used in gas sensors, biosensors, and other applications owing to its excellent optical features. In addition, there are reports that it is also used as an anode material in lithium-ion batteries because of physical advantages such as a broader surface and excellent ion storage amount compared to graphite [\u003cspan additionalcitationids=\"CR9 CR10 CR11 CR12 CR13\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The most commonly used methods for producing porous silicon include chemical methods, such as electrochemical etching in electrolyte solutions, and physical methods using large etching equipment, e.g., reactive ion etching (RIE) in vacuum environments [\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAmong them, electrochemical etching has been studied extensively because it allows the easy fabrication of porous silicon and offers advantages in process time and cost compared to other physical methods. This electrochemical etching technique includes directly applying a current in an electrolyte and etching using a self-electric potential generated through metal catalysts.\u003c/p\u003e \u003cp\u003eWhen a noble inert metal (e.g., Pt, Au, and Ag) comes into contact with a Si wafer, the flow of electrons and holes occurs due to a difference in work function. The interface is in the thermal equilibrium state, and electrochemical etching is carried out using the self-potential generated in this process [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThus far, many studies have suggested that metal catalyst etching (MICE) induces macroscopic changes in the etched morphologies depending on the composition and temperature of the etching solution and the type of catalyst metal [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Such changes in etched morphologies will be accompanied by changes in the physical and optical characteristics. Hence, structural changes must precede to induce various characteristic changes in porous silicon. This is closely related to the etching behavior. The hole is the majority carrier in p-type Si, and the etching behavior changes according to the behavior of the holes because the etching reaction originates from the recombination of holes and electrons. Therefore, the structural and optical characteristics of porous silicon vary with the etching behavior [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Nevertheless, the studies presented thus far on the electrochemical etching technique using metal catalysts focused on the application of devices based on porous silicon. Moreover, detailed studies are needed on the correlation between various characteristics of porous silicon manufactured by metal-induced chemical etching. This study examined the correlation between the morphological, electrical, and optical features of porous silicon prepared by MICE.\u003c/p\u003e"},{"header":"2. Experimental procedure","content":"\u003cp\u003eThe porous silicon was fabricated using a metal catalyst, and a p-type Si wafer with a resistivity of 0.005 Ω\u0026bull;cm was applied. Before MICE, piranha and HF cleaning were carried out to remove the organic contamination and native oxide layer. Platinum was used as a metal catalyst. A 300 \u0026micro;m-patterned metal catalyst was deposited approximately 5\u0026ndash;6nm thick by DC magnetron sputtering for 15. In this study, the p-type Si wafer has a work function of approximately 5.08 eV and a doping concentration of 2.05 \u0026times; 10\u003csup\u003e19\u003c/sup\u003e atoms/cm\u003csup\u003e3\u003c/sup\u003e. The work function of the platinum used as the catalyst was 5.93 eV [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Band bending occurs when these materials are in contact with each other. The difference between the Fermi energy and the highest state of the valence band was calculated to be 0.02 eV using Eq.\u0026nbsp;1. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the band structure of contact between platinum and p-Si. This contact shows ideal ohmic contact in which the carrier flow occurs easily at a low electric potential. Therefore, the depletion layer will be minimal or not occur at all [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The electrolytes included HF (49% diluted), DIW (deionized water), and hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e-30% diluted). The H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e content in the electrolytes was varied from 0.3 to 24.0%. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e lists the composition of each component in the solution.\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\u003eComposition of the electrolytes\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e# of Samples and electrolytes\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHF ratio\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDIW ratio\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0.30%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e48.51%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e51.19%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e3.00%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e44.10%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e52.90%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e5.10%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40.67%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e54.23%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e9.90%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e34.30%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e55.80%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e15.00%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e24.50%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e60.50%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e19.50%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17.15%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e63.35%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e22.50%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12.25%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e65.25%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e24.00%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9.80%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e66.20%\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\u003eMICE was carried out for 20 min without an electrical potential, and a current flowed spontaneously by the carrier behavior during MICE. This electrical potential was measured using a source meter (Keithley, 2425). The changes in the etched structure were observed by field-emission scanning electron microscopy (FESEM, Hitachi S-4300). Raman spectroscopy (Horiba Jobin Yvon LabRam HR) was conducted to examine the nanostructural characteristics. The optical features were analyzed using a spectrofluorophotometer (Dongwoo Optron RAM Boss) and confocal laser microscopy (Zeiss LSM 510 META).\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\({\\varvec{\\rho }}_{0}={\\varvec{N}}_{\\varvec{V}}\\varvec{e}\\varvec{x}\\varvec{p}\\left[\\frac{-({\\varvec{E}}_{\\varvec{F}}-{\\varvec{E}}_{\\varvec{V}})}{\\varvec{K}\\varvec{T}}\\right]\\)\u003c/span\u003e \u003c/span\u003e \u003cb\u003eEq.\u0026nbsp;(1)\u003c/b\u003e\u003c/p\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Morphological features\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows surface and cross-sectional SEM images of porous silicon etched for 20 minutes at various H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentrations. The etching morphologies changed according to the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e content (б). In the case of samples 2 and 3, the cross-section of the porous silicon exhibited a \u0026lsquo;sponge-like\u0026rsquo; structure, with pores several hundred nanometers in size. In the case of the etched surface, the etching reaction occurred uniformly within the Pt-deposited areas.\u003c/p\u003e \u003cp\u003eWhen the б was 22.5% (sample 7), the \u0026lsquo;sponge-like\u0026rsquo; structure disappeared, and micrometer-scale pores formed on the etched surface. This etching structure formed preferentially from the center region of the etched surface. The density of the etched structure tended to increase in outer regions, and the etched structure size decreased gradually.\u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, inhomogeneous etching also occurred at the non-coated region between two metal discs in the case of sample 7. These results suggest that changes in the distribution and amount of applied electrical potential occurred depending on the composition of the electrolytes. In the case of sample 8, a pseudo \u0026lsquo;sponge-like\u0026rsquo; structure formed again at the cross-section. Nanometer-scaled pores were observed at the inside of the etched structure, and the density of the etched structure decreased. When the б was increased, the rate of hole consumption was lower than its generation rate at the metal-deposited region. Consequently, the number of excess holes increases, and they diffuse from the etch tips to the outer region of the pore or non-coat region [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In addition, when the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration is high, the mobility of holes decreases, leading to the diffusion of excess holes that do not reach the metal deposition area across the surface of the silicon wafer. As a result, random etching occurs on the silicon surface. Hence, the distribution and magnitude of the applied electric potential change according to the etching site. These phenomena are caused by the stronger hydrogen bonds between H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e molecules than those in water molecules. Therefore, as \u0026lsquo;б\u0026rsquo; increases, the hydrogen bonds increase, and the bonding between the molecules in the liquid state will be stronger, increasing internal friction [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAn inhomogeneous distribution of etch rates occurred in the metal deposited area when the б was increased because of decreasing hole mobility. Inhomogeneous etching also occurred in non-coated areas. From the cross-sectional images of porous silicon, the vertically formed sponge structures gradually disappeared when б increased. According to Chartier et al., when the б is increased, holes are consumed on the outer walls of the etching pores, and the overall pore size will increase [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. As б increases, even using the same metal, the increased generation of holes results in a relatively stronger electric potential. These phenomena will cause \u0026ldquo;electropolishing,\u0026rdquo; where micropores rather than nanopores are formed. From this point, the thickness of the formed SiO\u003csub\u003ex\u003c/sub\u003e layer increases, and the etching rate will be lower [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Furthermore, saturated holes that fail to reach the deposition area diffuse into areas where the metal is not coated, causing etching even in the uncoated areas. On the other hand, the etching rate in these non-coated areas is lower than in the metal-coated areas. This has been attributed to a depletion layer between the silicon and the etching solution in the non-coated regions. Hence, the supplying pattern of holes is also changed when the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration is changed. These phenomena will cause changes in the etching behavior of porous silicon.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Electrical Features\u003c/h2\u003e \u003cp\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\u003eElectrical properties of the porous silicon prepared by metal-induced chemical etching\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEtchant temp.(K)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003e290 / 310\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e# of sample and electrolytes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio(б) (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e19.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e24.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCurrent Density (A/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e293 / 493\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e658 / 1173\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e667 / 1289\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e444 / 978\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e378 / 933\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e178 / 413\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e129 / 293\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e89 / 202\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eln J\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.68 / 6.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.49 / 7.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.50 / 7.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.10 / 6.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.93 / 6.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5.18 / 6.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4.86 / 5.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e4.49 / 5.31\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eY-intercept\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e17.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e20.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e18.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e17.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e17.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSlope /1000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;2.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;2.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026minus;3.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;3.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;4.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026minus;3.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026minus;3.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026minus;3.76\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eE\u003csub\u003ea\u003c/sub\u003e (290\u0026rarr;310K) (eV)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0.20\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.23\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.26\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.31\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e0.36\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.33\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.32\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.32\u003c/b\u003e\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\u003e \u003c/p\u003e \u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"443\" height=\"44\"\u003e\u003c/p\u003e\u003cp\u003eAs \u0026lsquo;б\u0026rsquo; increased, the activation energy increased from 0.20 eV to 0.36 eV. In the case of sample 5, the activation energy was maximum, and the activation energy decreased from this concentration. When the etching behavior was \u0026lsquo;pore formation,\u0026rsquo; the behavior of holes supplied from H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e was confined to the platinum deposition area. Furthermore, SEM showed that this resulted in a vertical \u0026lsquo;sponge-like\u0026rsquo; etching structure. Moreover, as the first step of the etching procedure, etching occurs only in a limited area. Therefore, the activation energy required for etching is expected to be lower. As the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration increased, the number of holes increased, and etching occurred even in the non-coated region, as shown by the SEM results. These results suggest an increase in activation energy [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The increase in activation energy is associated with changes in etching behavior.\u003c/p\u003e \u003cp\u003eAs shown in previous SEM results, when \u0026lsquo;б\u0026rsquo; was changed from 5.1\u0026ndash;22.5%, the etching structure within the platinum deposition area transformed from a vertical nanoscale to a 3D microscale. These changes showed that the etching behavior was changed from \u0026ldquo;pore formation\u0026rdquo; to \u0026ldquo;electropolishing.\u0026rdquo; During the etching process, the main reactions, such as the dissolution of silicon and the formation of SiO\u003csub\u003ex\u003c/sub\u003e layers, occur selectively depending on whether an overpotential occurs on the surface. This selective variation changes the reaction activation energy [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], which is related to the behavior of holes. The etching rate in the \u0026lsquo;pore formation\u0026rsquo; stage is determined by the Si dissolution occurring at the interface between the Si and the deposited metal. Moreover, in the \u0026ldquo;electropolishing\u0026rdquo; stage, the etch rate is determined dominantly by the formation and dissolution of the Si oxide film. In addition, the reaction activation energy is influenced by the overpotential within the reaction system and the diffusion of holes in the uncoated area. In electrolytes with relatively lower HF concentrations, the dissolution reaction of the anodic oxide film was not rapid. Therefore, as the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e content increased, the SiO\u003csub\u003ex\u003c/sub\u003e film remained even after the reaction in the etching behavior of \u0026ldquo;electropolishing\u0026rdquo; [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Such changes in surface characteristics caused variations in the optical properties based on the quantum structure. When \u0026lsquo;б\u0026rsquo; \u0026gt; 15%, although the absolute value of the current density decreases, the activation energy value was saturated above 0.3 eV. These phenomena mean the etching behavior persists in the \u0026ldquo;electropolishing\u0026rdquo; stage. As an oxide layer gradually accumulated on the surface during etching, it acted as an insulator, causing a potential drop and interfering with charge transfer. In the state where micrometer-scale etching structures formed, the reaction induced by randomly over-supplied holes led to the spread of defects acting as etching tips up to the uncoated areas. Consequently, the etching reaction of three-dimensional micrometer-scale structures will persist across the entire area exposed to the electrolyte [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The possibility of macropore formation increases when the conductivity of the electrolyte solution is lower than that of the Si wafer. If the doping concentration of Si is reduced, \u0026ldquo;electropolishing\u0026rdquo; behavior will occur at even lower \u0026lsquo;б\u0026rsquo; than observed in the present results. As etching progressed gradually, the Si wafer with a resistivity of 0.005 Ω\u0026bull;cm changed from semi-metallic to more insulating. Therefore, the formation of macropores occurred.\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e lists the activation energy calculated from the measured electrical potential and detailed results. The slope represents the etch rate, and the Y-intercept signifies the potential barrier [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. As \u0026lsquo;б\u0026rsquo; increased, the etch rate also increased under the same conditions. The contact between highly doped p-type Si and platinum exhibited ideal ohmic contact. Hence, there is a very thin potential barrier at the interface. As the temperature or \u0026lsquo;б\u0026rsquo; increases, more carriers can overcome the potential barrier, enhancing the tunneling phenomena. Therefore, even if the barrier increases, rapid changes in the etching behavior and increasing phenomena of etch rate were observed for the same process time.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Nanostructural features\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the Raman spectroscopy results of porous silicon according to the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio (б). The peaks were deconvoluted by Gaussian function to each of the spectra. The symmetric peak of bulk Si occurred dominantly at 521 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Furthermore, the broad peak at 480 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e represents the Transverse Optical (T.O) vibrations of the Si amorphous phase, while the region from 490 to 520 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to Si nanocrystallites[\u003cspan additionalcitationids=\"CR32\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. In addition, the various peaks were separated by Si vibrational movements. Among the several peaks, the SiO\u003csub\u003ex\u003c/sub\u003e peak was observed in the 430 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e region [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ed shows the calculated fractions for the three components (Si nanocrystals, amorphous areas, and SiO\u003csub\u003ex\u003c/sub\u003e), excluding the dominant bulk Si peak among the separated peaks in each region. Furthermore, the size of the Si nanocrystallite was calculated using Eq.\u0026nbsp;3 [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\text{D}=2{\\pi }\\sqrt{\\frac{B}{\\varDelta \\omega }}\\)\u003c/span\u003e \u003c/span\u003e \u003cb\u003eEq.\u0026nbsp;(3)\u003c/b\u003e\u003c/p\u003e \u003cp\u003ewhere ∆w is the shifting value in the Si nanocrystallite peak from the bulk silicon (521 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), and B is the full-width at half-maximum (FWHM) of bulk silicon, which is 2.0 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003enm\u003csup\u003e2\u003c/sup\u003e in this study. When б was varied from 3.0 to 24.0%, the size of the nc-Si changed from 3.0 to 4.6 nm, respectively. On the other side, the Si bulk peak only occurred in the case of sample 1. A sufficient etching reaction did not occur to form a Si quantum structure. Moreover, among the various separated peaks, the fraction of peaks related to the quantum structure, which includes the Si nanocrystallite, changed from 57 to 38.5% when б was varied. Although the changes were not continuous and uniform because the measurement was carried out in only a part of the entire region, there was a tendency for the fraction of the quantum structure to decrease when the б was increased. Furthermore, the volume fraction of SiO\u003csub\u003e2\u003c/sub\u003e was highest at 44.8% in the case of sample 4, and it gradually maintained again to approximately 24\u0026ndash;30% when the б \u0026gt; 15.0%. The volume fraction of the amorphous phase was also maintained around 28% in the б range. These results suggest that when the б \u0026gt; 9.9%, the etching behavior was maintained as \u0026ldquo;electropolishing,\u0026rdquo; and SiO\u003csub\u003e2\u003c/sub\u003e formation occurred preferentially over nc-Si formation in this б range. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e provides detailed results. These phenomena induced the transitions in the emission region or variations in emission intensity of the luminescence phenomenon based on the nanocrystals.\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\u003eDetailed data of the nanostructural features of the porous Si prepared by metal-induced chemical etching\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\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 \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample Etchant #\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio (б) (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e15.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e19.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e24.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003enc-Si (nm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e4.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAmorphous phase (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e25.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e14.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e28.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e28.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e25.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e28.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuantum structure (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e57.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e55.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e48.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e46.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e48.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e38.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e44.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e24.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e24.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e25.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e30.8\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 \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Optical features\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e presents the photoluminescence (PL) spectra of the MICE-prepared porous silicon. The maximum peaks were observed from 661 to 716nm when б was increased from 3.0 to 24.0%. These wavelengths corresponded to band gaps of 1.88 to 1.73 eV. In the case of sample 1, photoluminescence did not occur due to the insufficient existence of quantum structures referring to the Raman spectroscopy results. The PL intensity decreased gradually as б was increased. Hence, the etching behavior changes according to \u0026ldquo;δ.\u0026rdquo; The fraction of amorphous phase and SiO\u003csub\u003e2\u003c/sub\u003e increased when the etching behavior was \u0026lsquo;electropolishing,\u0026rsquo; while the fraction of silicon nanocrystals decreased, causing a decrease in PL intensity. Furthermore, the transition of etching behavior to electropolishing, leading to the coarsening of the etching structure, is also a cause of the decay of quantum structures. In the case of sample 3, the PL intensity was highest. According to the Raman spectra, this was associated with the second-largest volume fraction of the peak in the vibration of the quantum structure, which was 55.6%. In the case of sample 2, the quantum structure ratio was higher than that of sample 3. but the PL intensity observed in both cases is similar because the fraction of the amorphous phase is also high. On the other hand, in the case of sample 8, which exhibited the weakest PL intensity, the volume fraction of the peak in the vibration of the Si quantum structure ratio was lowest at 38.5%.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThis is related to the etching behavior. The formation of quantum structures contributing to luminescence is closely related to the etched morphologies. The mobility and behavior of holes also changed when the etching behavior was varied. Consequently, the etching morphologies changed with \u0026lsquo;б,\u0026rsquo; as observed by SEM. In addition, the quantum structures contributing to the PL phenomena were generally located at the etched surface. Hence, the positions of the quantum structure were selectively different with etched morphologies. When the etching behavior is \u0026ldquo;electropolishing,\u0026rdquo; vertical etching occurs as the etching process progresses, and the deposition metal, which serves to supply holes from H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, moves to a lower position. Consequently, the quantum structures formed by the anodic oxidation reaction exist at lower positions as the reaction proceeds [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. These phenomena interfere with the direct contribution of nanocrystals to photoluminescence, leading to a decrease in PL intensity. Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e lists the detailed results.\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\u003eDetailed results of the optical features of the porous Si prepared by metal-induced chemical etching\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample Etchant #\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio (б) (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e19.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e24.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003enc-Si size (nm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBand gap (eV)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.73\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMax. PL intensity (nm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e238\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e251\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e247\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e239\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e231\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e232\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e227\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAmorphous phase (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e28.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e25.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e28.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuantum structure (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e57.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e40.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e48.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e46.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e48.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e38.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e shows confocal laser microscopy images of porous silicon samples etched in solutions with varying H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentrations. In the case of sample 1, fluorescence characteristics were observed only in the regions where the interface between coated metal and Si substrate. As the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration increased, the area exhibiting fluorescence characteristics expanded gradually, starting from the platinum-silicon wafer interface. In the case of sample 5, the fluorescence characteristics appeared throughout the entire deposited area.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the case of sample 6, the fluorescence characteristics were observed in the metal-deposited areas and other parts. This is because the behavior of electrons and holes changes with the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration. The supply of holes increases as б increases, leading to a surplus of holes over the amount needed for the etching reaction at the metal-silicon interface. Therefore, the excess holes diffuse into the non-coated areas of the silicon wafer, where they generate additional electric potential, causing etching and generating random quantum structures on the surface. Consequently, fluorescence characteristics appear even outside the metal-deposited region [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWhen the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration was 24.0%, most areas exhibited fluorescence characteristics. These observations were attributed to the variation in etching behavior and changes in the distribution of nanostructures due to the varying H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003ePorous silicon prepared by MICE according to the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e content showed a change in the activation energy depending on the etching behavior. As the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e content increased, the etching behavior changed from \u0026ldquo;pore formation\u0026rdquo; to \u0026ldquo;electropolishing,\u0026rdquo; leading to a change in the etching morphologies. When the etching behavior changed, the etching morphologies varied from a \u0026lsquo;sponge-like\u0026rsquo; structure to the 3D micro-pores. Furthermore, when the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration exceeded 19.5%, the etching reaction occurred in the platinum deposition area and non-coated areas. This result was attributed to the change in the supplying behavior of holes throughout the entire surface as the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration increased, leading to diffusion into the non-coated areas. The activation energy also changed according to the etching behavior. The reaction activation energy changed from 0.2 to 0.36 eV when the etching behavior shifted from \u0026ldquo;pore formation\u0026rdquo; to \u0026ldquo;electropolishing.\u0026rdquo; The activation energy was saturated at approximately 0.3 eV when the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration was 15.0%, and the etching structure appeared in the mixed form of sponge and three-dimensional micro-pores when the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration was increased further.\u003c/p\u003e \u003cp\u003eWhen the etching behavior was changed, the Raman vibration related to the SiO\u003csub\u003ex\u003c/sub\u003e and Si amorphous phase in the overall phase was increased. When the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio was increased, the PL characteristics in the wavelength range changed from 661 nm to 716 nm, and the size of the nanocrystals decreased from 4.6 nm to 3.0 nm. The luminescence intensity decreased as the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio increased. Hence, the quantum structure contributing to the emission was gradually positioned at the lower etched region as the etching behavior changed. Furthermore, as etching progresses, the increase in volume fraction of the Si amorphous and SiO\u003csub\u003ex\u003c/sub\u003e phases was also considered to influence the decrease in PL intensity. The fluorescence characteristics on the etched surface varied as the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio increased. The fluorescence characteristics that occurred primarily at the interface between silicon and platinum spread throughout the platinum-coated area and even to the non-coated areas as the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e concentration increased. The nanostructural and optical features of porous silicon prepared by MICE were dependent on the variations in the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThe authors of this work confirm that the results of this study do not involve humans or animals in this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot Applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCorresponding author Professor Hyun Soon Park grants permission to publish this manuscript in the journal ‘Silicon’ if it is accepted.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and / or analyzed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported by an Inha University Research Grant (INHA-67987).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHyo Han Kim is a Ph.D candidate under Professor Hyun Soon Park and a researcher at ULVAC, where he conducted experiments, analyses, and drafted the manuscript. Sang ho Lee is Hyo Han Kim's manager at ULVAC and reviewed the draft together with Professor Park HS. Professor Hyun Soon Park is Hyo Han Kim's advisor, provided funding support for the research, and reviewed and revised the manuscript draft.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank Professor Dae Yong Jung of Inha University for providing the pre-treatment equipment for the samples.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCullis AG, Canham LT (1991) Visible light emission due to quatum size effects in highly porous crystalline silicon. Nature 353:335-338 \u003c/li\u003e\n\u003cli\u003eCullis AG, Canham LT, Calcott PDJ (1997) The structural and luminescence properties of porous silicon. J Appl Phys 82:909-965 \u003c/li\u003e\n\u003cli\u003eDelley B, Steigmeier EF (1995) Size dependence of band gaps in silicon nanostructures. 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Phys Chem Chem Phys 24:11206-11212\u003c/li\u003e\n\u003cli\u003eChartier C, Bastide S, Levy-Clement C (2008) Metal-assisted chemical etching of silicon in HF-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Electochim Acta 53:5509-5516 \u003c/li\u003e\n\u003cli\u003eIslam MN, Ram SK, Kumar S (2007) Band edge discontinuities and carrier transport in c-Si/porous silicon heterojunctions. J Phys D Appl Phys 40:5840-5846\u003c/li\u003e\n\u003cli\u003eZhang XG, Collins SD, Smith RL (1989) Porous silicon formation and electropolishing of silicon by anodic polarization in HF solution. J Electochem Soc 136:1561-1565\u003c/li\u003e\n\u003cli\u003eSimmons JG (1963) Generalized formular for the electric tunnel effect between similar electrodes separated by a thin insulating film. J Appl Phys 34:1793-1803\u003c/li\u003e\n\u003cli\u003eWang WY, Lee TH, Reed MA (2005) Intrinsic electronic conduction mechanisms in self-assembled monolayers In: Introducing Molecular Electronics, pp.275-300, Springer, Berlin\u003c/li\u003e\n\u003cli\u003eSui Z, Leong PP, Herman I (1992) Raman analysis of light-emitting porous silicon. App Phys Lett 60:2086-2088\u003c/li\u003e\n\u003cli\u003eHe Y, Yin CY, Cheng G, Wang L, Liu X, Hu GY (1994) The structure and properties of nanosize crystalline silicon films. J Appl Phys 75:797-803\u003c/li\u003e\n\u003cli\u003eSirenko AA, Fox JR, Akimov IA, Xi XX, Ruvimov S, Liliental-Weber Z (2000) In situ raman scattering studies of the amorphous and crystalline Si nanoparticles. Solid State Commun 113:553-558 \u003c/li\u003e\n\u003cli\u003eMcMillan P (1984) Structural studies of silicate glasses and melts-applications and limitations of raman spectroscopy. Am Mineral 69:622-644\u003c/li\u003e\n\u003cli\u003eSong M, Fukuda Y, Furuya K (2000) Local chemical states and microstructure of photoluminescent porous silicon studied by means of EELS and TEM. Micron 31:429-434\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"silicon","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scon","sideBox":"Learn more about [Silicon](https://www.springer.com/journal/12633)","snPcode":"12633","submissionUrl":"https://submission.nature.com/new-submission/12633/3","title":"Silicon","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Metal-induced chemical etching, Porous silicon, Etching behavior, Anodization, Optical properties","lastPublishedDoi":"10.21203/rs.3.rs-4380378/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4380378/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePorous silicon (PS) was produced by the metal-induced chemical etching of p-type Si wafers. Patterned platinum dots (~\u0026thinsp;300 \u0026micro;m) were deposited on a Si wafer by DC magnetron sputtering for 15 s. When the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e fraction in the etchants consisting of HF and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e was increased from 0.3 to 24%, the etching behavior changed from \u0026ldquo;pore formation\u0026rdquo; to \u0026ldquo;electropolishing.\u0026rdquo; The etching reaction activation energy also changed from 0.20 to 0.36 eV in the ln J\u0026ndash;K(current\u0026ndash;etchant temperature) relationships. The etched morphologies exhibited different structures, such as nano-scaled sponge-like and 3D micro-scaled pore structures, according to the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio. The etched layers contained a Si quantum structure, amorphous Si phase, and SiO\u003csub\u003ex\u003c/sub\u003e. These phase ratios changed according to the etching behavior. The Si nanocrystallite size changed from ~\u0026thinsp;3.0 to 4.6 nm, emitting optical features in the band gap range of 1.73 to 1.88 eV. The fluorescence region varied according to the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e ratio. The fluorescence preferentially occurred at the interface between the metal circle and Si wafer in the case of etched PS by an etchant containing a lower hydrogen peroxide ratio. In contrast, the fluorescence increased in the non-coated region from 19.5 to 24.0%.\u003c/p\u003e","manuscriptTitle":"Morphological and Electrical Features of Porous Silicon Prepared by Metal-Induced Chemical Etching","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-07 17:43:53","doi":"10.21203/rs.3.rs-4380378/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-08-06T11:57:50+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-17T12:29:37+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-15T16:02:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"58292807732902452678038789588552462657","date":"2024-07-12T13:37:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"97212506112140767323926632007005431052","date":"2024-07-11T08:47:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"502114212896530200487561039726930107","date":"2024-06-17T03:07:34+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-30T14:03:28+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-05-21T11:42:18+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-21T11:42:18+00:00","index":"","fulltext":""},{"type":"submitted","content":"Silicon","date":"2024-05-07T05:30:20+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"silicon","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scon","sideBox":"Learn more about [Silicon](https://www.springer.com/journal/12633)","snPcode":"12633","submissionUrl":"https://submission.nature.com/new-submission/12633/3","title":"Silicon","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e1711971-b3e8-4c33-af3b-315fa39679cb","owner":[],"postedDate":"June 7th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-09-30T16:03:04+00:00","versionOfRecord":{"articleIdentity":"rs-4380378","link":"https://doi.org/10.1007/s12633-024-03151-0","journal":{"identity":"silicon","isVorOnly":false,"title":"Silicon"},"publishedOn":"2024-09-27 15:57:33","publishedOnDateReadable":"September 27th, 2024"},"versionCreatedAt":"2024-06-07 17:43:53","video":"","vorDoi":"10.1007/s12633-024-03151-0","vorDoiUrl":"https://doi.org/10.1007/s12633-024-03151-0","workflowStages":[]},"version":"v1","identity":"rs-4380378","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4380378","identity":"rs-4380378","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}