Optical and fractal properties of sputter deposited TiO2 films

Optical and fractal properties of sputter deposited TiO2 films | 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 Optical and fractal properties of sputter deposited TiO 2 films Reza Shakoury, Elaheh Nahvifard, Ali Arman, Bandar Astinchap, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1554124/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract In this study, TiO 2 films were deposited on the glass and silicon substrates at different pressures using a DC magnetron sputtering system. Surface topography, fractality, particle size, transparency spectra, and roughness of the deposited films were analyzed through atomic force microscopy (AFM) in non-contact mode and spectrophotometer (UV-visible) analysis. The surface morphology, absorption spectra, transparency, and conductivity of the films were studied through analytical and mathematical relations, including fractal and multifractal dimensions of the films. The pressure influenced the particle size leading to the changes in the surface roughness and fractality of the films. When the working pressure increased above 8×10 − 3 Torr, the nonuniformity in the distribution of surface properties and multifractality increased. Additionally, using optical data and the Tauc ́s method, their energy gap was calculated. It was revealed that the TiO 2 coatings have a relatively large energy gap of ~ 4eV, probably due to their small grain size. TiO2 Magnetron sputtering Optical properties AFM Fractal analysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Thin films have unique properties that are significantly different from their corresponding properties in the bulk state. This difference is often due to their physical dimensions (surface to volume ratio), geometric shape, and microstructure. However, a thin film with leveraged characteristics can be synthesized by modifying its properties to a great extent, which is the basis for developing thin film applications in various industries [ 1 ]. Submicron thin films are widely used in Micro-Electro-Mechanical Systems (MEMS), microelectronic integrated circuits, and semiconductors, as well as optical, magnetic, and quantum interference devices. On the other hand, thin films with a large surface-to-volume ratio are used in solar cells for photovoltaic conversion, shielding layers, inactivation layers, etc. Therefore, it is expected that the application of thin films will extend even further by developing many products in the form of a thin film in the near future. There are different methods for the mass and easy production of thin films and nanostructures. The differences between these methods are mainly in the mechanism of material transfer from source to the substrate, transfer medium, working pressure and deposition sensitivity, and simplicity of work [ 2 – 8 ]. In recent years there has been a surge of interest in nanostructured films of metals and their oxides due to their unique mechanical, chemical, optical, and structural properties [ 9 – 16 ]. Meanwhile, titanium and its associated oxides have been reported to be environmentally friendly and cost-effective materials that exhibit good chemical and optical stability, high corrosion resistance in 3.5% NaCl solution, and insolubility in the water [ 17 – 20 ]. Titanium dioxide (TiO 2 ), or titania, shows n-type semiconductor properties at room temperature because of the formation of oxygen voids or titanium atoms within the lattice; each of those defects causes the formation of donor type semiconductors [ 21 – 23 ]. The TiO 2 exists in nature with three different crystal structures; anatase, rutile, and brookite, where anatase and rutile have a tetragonal structure while brookite has an orthorhombic structure [ 24 – 27 ]. Among the three natural mineral phases of titanium dioxide, the rutile is the most stable and dense phase, while the anatase phase is the least dense. The rutile structure is found naturally in volcanic rocks or rocks exposed to high temperatures and pressures. Rutile is more likely to be found in such environmental conditions due to its low molecular volume than the other two structures. Natural rutile contains about 10% iron, a large amount of niobium, and tantalum. In fact, anatase and brookite are polymorphs of rutile formed by the cooling of igneous rocks [ 28 ]. Additionally, metastable anatase and brookite phases can be formed at temperatures above 600°C. The brookite phase is thermodynamically unstable, and it cannot be found independently, though it exists alongside other titanium dioxide phases. The two most commonly used titanium dioxide crystal structures are the rutile and anatase structures. In the rutile structure, the recombination rate of the charges created by light activity is much higher than that of anatase. This causes the low charge transfer of the rutile structure to the reactants and low efficiency, which is the reason to use this material in color compounds. In contrast, the anatase structure with low recombination, high charge transfer, and consequently, high efficiency can be used as a material with suitable optical activity [ 29 ]. Therefore, the application and efficiency of TiO 2 are strongly influenced by its crystal structure, as well as its particle size and shape [ 8 , 28 ]. Qiu et al. [ 30 ] reported the enhanced photocatalytic efficiency and optical absorption of TiO 2 films through doping with ZrFe 2 O 4 by sol-gel method. When studying the thermal stability of e-beam deposited TiO 2 coatings, it has been shown that the optical loss of coatings synthesized by e-beam deposition decreased with annealing temperature [ 31 ]. Accordingly, great efforts are made to synthesize TiO 2 nanoparticles with controlled size, shape, and porosity to be used in thin films, ceramics, composites, and catalysts [ 25 , 32 – 35 ]. Other applications of TiO 2 include a wide energy gap in all its crystalline forms, a good position of the conduction and valence bands, and chemical stability, which is widely used in photocatalytic and water decomposition applications. Since it has hydrophilic properties, this material can also be used to prepare self-cleaning surfaces [ 2 , 24 , 34 , 36 ]. Moreover, the ability of TiO 2 to absorb ultraviolet light has led to its application in cosmetics, especially sunscreens, to prevent skin damage. Owing to its unique optical and electrical properties, TiO 2 is used in the manufacturing of solar cells, chemical sensors, and optical coatings. It has also been used to extend medical applications such as artificial heart valves and dental implants [ 36 , 37 ]. This substance causes the uniformity of bone cells between medical implants and bone. TiO 2 in solution or suspension can also break down proteins containing the aminoacid proline in places where proline is present [ 38 ]. However, no studies have been performed on the effect of working pressure on the surface morphology of thin films by the multifractal method and its relationship with the optical energy gap. Therefore, the present study is primarily based on atomic force microscopy (AFM) measurements of magnetron sputtered TiO 2 films. We utilized AFM and spectrophotometer measurements to study the effect of inward gas flux changes on the structural, morphological, and optical properties of the TiO 2 films. Furthermore, optical data and the Tauc ́s method were used to calculate the energy gap of deposited films. 2. Materials And Methods A DC magnetron sputtering system with a cylindrical glass chamber was used to deposit TiO 2 films. The chamber consisted of two electrodes facing each other, one at the bottom with a larger radius (location under the films) and the other at the top with a radius of 9 cm connected to the DC source. A schematic of the deposition chamber is shown in Fig. 1 . Glass and silicon substrates were first cleaned in soap solution and then in an ultrasonic bath by immersing in acetone for 5 min. Then after drying, the substrate wafers were inserted into the chamber and placed on the grounded electrode. Oxygen and argon gases were introduced into the chamber with a flow rate of 4 sccm and 1 sccm, respectively. A mass flow controller (MFC) was used to adjust the working pressure of the chamber. A pure titanium target was sputtered by applying a constant power of 400 W in the medium of argon and oxygen to reactively deposit titanium oxide thin films. Detailed information on deposition parameters is listed in Table 1 . Table 1 The process parameters for fabricating the films. TiO 2 film Sputtering parameters Thickness (nm) Base pressure (Torr) Working pressure (Torr) Power density (W/cm 2 ) #1 10 − 5 6.0×10 − 3 400 481 #2 10 − 5 8.0×10 − 3 400 499 #3 10 − 5 1.0×10 − 2 400 491 #4 10 − 5 1.2×10 − 2 400 478 In order to statistically study the surface topography and roughness of the deposited films, an atomic force microscope (NT-MDT model BL022) in non-contact mode was used. The measurements were conducted on the 5×5 µm 2 area of the films. Using the spectrophotometer (Hitachi, model U-3501), the transparency spectra of the films were measured in the range of 300 nm to 900 nm. Subsequently, using this data, the absorption spectra of the films were drawn, then the energy gap was calculated using the Tauc ́s method [39] as follows; When a light beam enters a matter, the intensity of the output light is expressed by Beer-Lambert law, as follows; $$I={I}_{0}{e}^{-\alpha d}$$ where I is the intensity of the transmitted light, I 0 is the intensity of the incident light, d is the thickness of the layer, and α is the linear absorption coefficient of the material. From the above equation, the absorption coefficient can be calculated, which is used to obtain the energy gap in the Tauc ́s method. $$\alpha =\frac{1}{d}Ln\left(\frac{1}{T}\right)$$ The T here is the transmittance which is defined as the fraction of transmitted intensity to incident intensity. The relationship between the absorption coefficient and the photon energy is expressed as follows: $${\left(\alpha h\nu \right)}^{n}=A\left(h\nu -{E}_{g}\right)$$ where, \({E}_{g}\) is the energy gap of matter, \(h\nu\) is the photon energy, and A and n are constant coefficients. It is n = 2 for indirect transitions and n = 0.5 for direct circuits. By plotting the variation curve n ( \(\alpha h\nu\) ) in terms of \(h\nu\) and fitting the straight line in the linear range up to ( \(\alpha h\nu\) ) = 0, the energy gap value can be estimated. 3. Results And Discussion The surface features strongly influence the optical transmission and absorption processes and explain their behavior in the wide interval of wavelengths. On the other hand, the TiO 2 energy gap value substantially affects the optical processes for higher energies of photons (for wavelengths below 200 nm). The combination of multifractal analysis, as well as optical transmission and absorption processes, provides valuable information to explain the importance of optical processes in the growth of TiO 2 layers. Figure 2 shows the AFM images of titanium dioxide films recorded at a 5×5 µm 2 scale. The AFM images show that the TiO 2 nanoparticles were formed, and the growth of the layers followed the island growth model (Volmer–Weber). It can be seen that by increasing the input flux, the particle size distribution was changed, leading to changes in the surface roughness. Figure 3 shows the particle size distribution diagram. We know that as the working pressure increases, the density of the plasma on the substrate surface increases, which in turn increases the rate of nucleation and the rate of growth of the nuclei. At the same deposition time, increasing the nucleation rate resulted in an increase in the thickness of the layers, which was confirmed by the thickness measurement results reported by the quartz crystal. When the working pressure was 6×10 − 3 Torr, the average particle size was measured to be 52 nm while with increasing the working pressure to 8×10 − 3 , and then 1.0×10 − 2 , and finally 1.2×10 − 2 , the particle size was increased to 58, 60, and 62 nm, respectively. This indicates that the increase in the growth rate of the nuclei leads to a slight increase in the particle size formed in the plasma and accumulated on the surface, which was confirmed by the particle size distribution diagrams obtained from the images. The roughness values were varied between 1.59 nm and 1.73 nm; as for the lowest pressure, the average roughness was 1.7 nm, while it decreased to 1.65 and then to 1.58 nm with increasing the working pressure. On the other hand, further increasing the working pressure to 1.2×10 − 2 led to an increase in the roughness to 1.73 nm. Therefore, no clear relation between the roughness and working pressure was found. However, surface parameters such as maximum height and the total height of roughness profile as well as particle distribution of surface particles might lead to such a result [ 40 ]. The results of fractal analysis of the TiO 2 films are presented in Fig. 4 . The multifractal singularity spectra f (α) (Fig. 4 (a)) and generalized fractal dimension Dq (Fig. 4 (b)) indicate well developed multifractal properties of the h ( x,y ) function determined from the AFM images for all TiO 2 films. The profile of the f (α) function indicates a decreasing trend in the surface fractality (over) with increasing the working pressure from 6×10 − 3 Torr to 8×10 − 3 Torr (film #1 and #2). On the other hand, the surface fractality was increased dramatically by further increasing the working pressure from 8×10 − 3 to 1.2×10 − 2 Torr (films #2 - #4). The width of the f (α) function corresponds to a broader range of surface features (see. Figure 4 (a)). Therefore, comparing the multifractal spectra of deposited TiO 2 films reveals a broadening of f (α) with the working pressure above 8×10 − 3 Torr, which can be attributed to the increasing non-uniformity in the distribution of surface features at higher pressures. As shown in Fig. 4 (a), for the working pressure of 6.0×10 − 3 Torr, the left arm of the curve is longer, which indicates that larger nanoparticles were identified on the surface of this layer. However, as the working pressure increased, the curves changed, and the right arm of the curves became taller, indicating that smaller nanoparticles outperformed larger nanoparticles in determining the surface behavior of the layers. As shown in Fig. 4 (b), an identical conclusion can be deduced from the trend of generalized fractal dimension Dq . Here, the slope of the Dq function is associated with the fractality of the surface. Increasing the working pressure from 6×10 − 3 Torr to 8×10 − 3 Torr (films #1 and #2) led to a slight decreasing fractality, while a further increase in the pressure resulted in a significant increase in multifractality (films #2 - #4). These results are in good agreement with the values of (α max -α min ) and ( Dq max - Dq min ) in which the minimum was assigned to film #2 (Fig. 4 (c)), whereas, for the higher working pressures above 8×10 − 3 Torr, an increase in the multifractality was observed. The bigger the value of (α max - α min ), the higher the h ( x,y ) fluctuations are expected. The h ( x,y ) fluctuations detected by the multifractal singularity spectra were also the smallest for film #2. Another technique that was used further to describe the surface morphology of the deposited layers was Minkowski Functionals analysis. Minkowski boundary and Minkowski connectivity curves for all samples were calculated using the Gwyddion software. The curves obtained from the analysis of 4 samples are illustrated in Fig. 5 . The curves show that the Minkowski boundary and Minkowski connectivity are functions of working pressure. It was observed that the maximum boundary was obtained for sample 2. These results indicate the nanoparticles were placed on the surface so that they have the most boundaries. It is known that the Minkowski connectivity describes the measure of the number of connections in the nanoparticles pattern by analyzing the relationship between connected and disconnected pixels in an image. Also, as can be seen, the minimum and maximum of the Minkowski connectivity curve for sample #2 are higher than others. Therefore, the connection between nanoparticles in sample #2 was dominant, and the high connection occurs for larger nanoparticles at the surface of samples #1 and #2 compared to samples #3 and #4. Figure 6 . depicts the transmission and absorption spectra of the TiO 2 films in the visible region, derived from the dominant relationships between the optical spectra (transmission, absorption, and reflection). The films exhibited high absorption edges for wavelengths above 350 nm, which can be confirmed by a shift in their optical spectra (absorption edges) to higher wavelengths by increasing the working pressure. The minimum and maximum transparency in the films were almost constant, about 50% and 90%, respectively. It is notable that the optical behavior of #1 and #4 films, which were prepared at the lowest and highest pressures, respectively, were almost identical, while there was a slight phase shift in the wavelength of films #2 and #3. Therefore, it can be concluded that they exhibited similar transmittance and absorbance. This is in accordance with the changes in the surface roughness obtained from the AFM data. In a semiconductor material, the dependence of the absorption of the UV-visible radiation can be determined by the electronic transitions between the valence band and the conduction band. Therefore, the optical properties of semiconductors can be modified by controlling the band gap energy. On the other hand, the band gap energy in thin films strongly depends on the surface roughness and correspondingly on the fractal features of the coating. As discussed above, the Tauc ́s equation was used to determine the magnitude of the bandgap in TiO 2 films. This is possible by analyzing the data in Fig. 6 , n (ahʋ) in terms of hʋ, and extrapolating the values obtained in the high energy region with the horizontal axis. The closer the value of this parameter to zero, the higher the conductivity; thus, the better the semiconductor or non-conductive properties of the material. The results of this analysis are given in Fig. 7 . The energy gap of layers was found to be 3.98, 3.95, 4.03, and 4.00 eV for samples #1, #2, #3, and #4, respectively. It is notable that the energy gap of all TiO 2 films was in the vicinity of 4.00 eV, while the slight variation can be attributed to the changes in the working pressure. The results show that the lowest energy gap is related to the layer with the lowest ∆α, indicating that the surface complexity affected the energy gap. As we know, several factors can influence the energy gap of semiconductors. For instance, the energy gap value strongly depends on the crystal structure (such as defects, charged impurities, disorder at the grain boundaries), morphology (such as roughness, fractality, particles shape, and particles quantum size), the thickness of layers, and chemical composition of the material. Here, our aim was to study the effect of the surface morphology of the films on their energy gap. The results showed that increasing the multifractality of the films increased their energy gap. The high energy gap of the deposited layers can be ascribed to the multifractal properties of their surface, the small nanoparticle size (see particle size distribution diagram in Fig. 3 ). The energy gap determined by the Tauc ́s method is not very sensitive to changes in working pressure, as the Eg value is influenced mainly by material properties. The high absorption of wavelengths under 200 nm can be observed in Fig. 6 (b) for all structures, which was closely related to Eg = 4 eV determined by the Tauc ́s method for the TiO 2 layers. The development of surface features shows significant sensitivity of multifractal behavior on working pressure (see Fig. 4 (c and d). The modification of surface features by applied forming steps (revealed by multifractal methods) directly influenced the spectral transmission and absorption processes. The shifts of spectral transmittance (Fig. 6 (a)) and absorbance (Fig. 6 (b)) curves directly correlated with the trends of multifractal parameters determined from the AFM h ( x , y ) functions. The multifractal analysis provides valuable information about the surface properties and can directly explain the spectral absorption and transmission processes. Conclusion In this research, titanium dioxide films were deposited at different working pressures utilizing a magnetron sputtering system. The surface morphology and optical properties of TiO 2 films were investigated. According to the measurement of the crystal thickness gauge installed on the device, it was shown that the thickness of the TiO 2 films was varied with the pressure where the optimum pressure of 8×10 − 3 Torr was found for film #2 with the maximum thickness. Also, multifractal properties synergistically interacted with the development of the thickness of the films during the deposition. Investigation of AFM results revealed that particle size was changed with the pressure leading to the changes in the surface roughness and fractality of the films. Additionally, the nonuniformity in the distribution of surface properties and multifractality increased by raising working pressures. The changes in the thickness of the films were also evident in the optical spectra, wherein film #2 exhibited the lowest transmission while films #1 and #4 showed the highest transmission values. Also, it was found that by increasing the working pressure, absorption edges shift to higher wavelengths and possess high values for wavelengths greater than 350 nm. The energy gap and minimum and maximum transparency of the TiO 2 layers were less sensitive to changes in the working pressure. Using the Tauc ́s method, the energy gap of the films was calculated to be ~ 4eV. Such a large energy gap can be attributed to the small grain size of TiO 2 coatings. Eventually, the obtained results from the multifractal analysis showed that at the working pressure of 8.0×10 −3 Torr, the layers have the lowest ∆α and, therefore, the least complexity, as well as the lowest energy band gap. Declarations Acknowledgment We acknowledge the financial support of the Ministry of Industry and Trade of the Czech Republic, grant no. FV40238. Disclosure statement No potential conflict of interest was reported by the authors. Credit author statement R. Sh. & E. N. : Conceptualization and analyses; A. A, S. 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Eng. 33 (10), 779–786 (2017) Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 19 Apr, 2022 Reviewers invited by journal 18 Apr, 2022 Editor invited by journal 15 Apr, 2022 Editor assigned by journal 15 Apr, 2022 First submitted to journal 13 Apr, 2022 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-1554124","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":99469573,"identity":"03dfa981-466c-4e6b-8a07-e6189b5aff6c","order_by":0,"name":"Reza Shakoury","email":"","orcid":"","institution":"Imam Khomeini International University Faculty of Science","correspondingAuthor":false,"prefix":"","firstName":"Reza","middleName":"","lastName":"Shakoury","suffix":""},{"id":99469574,"identity":"e13f9be7-423c-4106-bae9-31fabf10cb06","order_by":1,"name":"Elaheh Nahvifard","email":"","orcid":"","institution":"Imam Khomeini International University Faculty of Science","correspondingAuthor":false,"prefix":"","firstName":"Elaheh","middleName":"","lastName":"Nahvifard","suffix":""},{"id":99469575,"identity":"f9be8a71-5268-44f2-808f-2062dac332d0","order_by":2,"name":"Ali Arman","email":"","orcid":"","institution":"ACECR: Academic Center for Education Culture and Research","correspondingAuthor":false,"prefix":"","firstName":"Ali","middleName":"","lastName":"Arman","suffix":""},{"id":99469576,"identity":"3a1c9940-e777-47af-81cc-b780ed1c1fa9","order_by":3,"name":"Bandar Astinchap","email":"","orcid":"","institution":"University of Kurdistan","correspondingAuthor":false,"prefix":"","firstName":"Bandar","middleName":"","lastName":"Astinchap","suffix":""},{"id":99469577,"identity":"fd0b48a0-a910-4416-8dcf-e6208c5fabc7","order_by":4,"name":"Stanislav Jurečka","email":"","orcid":"","institution":"University of Zilina: Zilinska univerzita v Ziline","correspondingAuthor":false,"prefix":"","firstName":"Stanislav","middleName":"","lastName":"Jurečka","suffix":""},{"id":99469578,"identity":"579acd91-4219-486e-8ae8-18e7b1d95f25","order_by":5,"name":"Mohsen Mardani","email":"","orcid":"","institution":"ACECR: Academic Center for Education Culture and Research","correspondingAuthor":false,"prefix":"","firstName":"Mohsen","middleName":"","lastName":"Mardani","suffix":""},{"id":99469579,"identity":"d212acb9-2dbf-48f6-9fd6-912c9dc1af48","order_by":6,"name":"Ghasem Amraee Rad","email":"","orcid":"","institution":"ACECR: Academic Center for Education Culture and Research","correspondingAuthor":false,"prefix":"","firstName":"Ghasem","middleName":"Amraee","lastName":"Rad","suffix":""},{"id":99469580,"identity":"c1fe1d7a-c4a5-4e43-a10d-aeb19ec3b594","order_by":7,"name":"Saeed Mirzaei","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0002-1905-4741","institution":"Brno University of Technology: Vysoke uceni technicke v Brne","correspondingAuthor":true,"prefix":"","firstName":"Saeed","middleName":"","lastName":"Mirzaei","suffix":""}],"badges":[],"createdAt":"2022-04-13 11:47:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1554124/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1554124/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":20571839,"identity":"ae75765f-dddf-4884-8566-54cd8817acea","added_by":"auto","created_at":"2022-04-20 18:58:36","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":16951,"visible":true,"origin":"","legend":"\u003cp\u003eThe sketch of the deposition chamber.\u003c/p\u003e","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1554124/v1/89fa27ae3c9099e48ffa6c36.jpg"},{"id":20572327,"identity":"e3c75b8c-f905-43dc-86ce-6a9d1dfa38cc","added_by":"auto","created_at":"2022-04-20 19:08:36","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":169572,"visible":true,"origin":"","legend":"\u003cp\u003eThe AFM images of TiO\u003csub\u003e2\u003c/sub\u003e films a) #1, b) #2, c) #3 and d) #4 recorded at 5×5 µm\u003csup\u003e2\u003c/sup\u003e surface area.\u003c/p\u003e","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1554124/v1/39eb287622176fa3faa002c2.jpg"},{"id":20571840,"identity":"ecb2f68f-4f2a-4c5f-b1b9-78ae23735d60","added_by":"auto","created_at":"2022-04-20 18:58:36","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":109939,"visible":true,"origin":"","legend":"\u003cp\u003eThe particle size distribution diagram of TiO\u003csub\u003e2\u003c/sub\u003e films a) #1, b) #2, c) #3 and d) #4 recorded at 5×5 µm\u003csup\u003e2\u003c/sup\u003e surface area.\u003c/p\u003e","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1554124/v1/8abe735d5b47720c37d2a58d.jpg"},{"id":20572244,"identity":"5f5a5d3d-dee1-44f6-a527-8495cb944c85","added_by":"auto","created_at":"2022-04-20 19:03:36","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":231114,"visible":true,"origin":"","legend":"\u003cp\u003eThe results of multifractal analysis obtained from AFM scans of TiO\u003csub\u003e2\u003c/sub\u003e films #1, #2, #3, #4: (a) multifractal singularity spectra \u003cem\u003ef\u003c/em\u003e(α); (b) generalized fractal dimensions \u003cem\u003eDq\u003c/em\u003e; (c) (α\u003csub\u003e max\u003c/sub\u003e-α\u003csub\u003emin\u003c/sub\u003e) and (d) (\u003cem\u003eDq\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e - \u003cem\u003eDq\u003c/em\u003e\u003csub\u003e\u003cem\u003emin\u003c/em\u003e\u003c/sub\u003e).\u003c/p\u003e","description":"","filename":"Fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1554124/v1/fc3e6fb2bfd4ecb9f10d71ef.jpg"},{"id":20571841,"identity":"f806783e-702f-4845-82ed-ec1eb93567f8","added_by":"auto","created_at":"2022-04-20 18:58:36","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":95172,"visible":true,"origin":"","legend":"\u003cp\u003eThe results of Minkowski Functionals analysis obtained from AFM images of TiO\u003csub\u003e2\u003c/sub\u003e films S1, S2, S3, S4: (a) Minkowski boundary (S); (b) Minkowski connectivity (χ);\u003c/p\u003e","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1554124/v1/bac9ba1972df5c939850a0a3.jpg"},{"id":20571845,"identity":"2133b39b-4c52-4bc5-9df1-a870007b739d","added_by":"auto","created_at":"2022-04-20 18:58:36","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":149867,"visible":true,"origin":"","legend":"\u003cp\u003eTransmittance (a) and absorbance (b) spectra of TiO\u003csub\u003e2\u003c/sub\u003e thin films deposited at different pressures.\u003c/p\u003e","description":"","filename":"Fig6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1554124/v1/d947e34336ddd7a3e45fe565.jpg"},{"id":20571843,"identity":"487af828-06f8-4264-ae01-8d07db6d6275","added_by":"auto","created_at":"2022-04-20 18:58:36","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":192368,"visible":true,"origin":"","legend":"\u003cp\u003eTauc plot for: film #1 (481 nm); film #2 (499 nm), film #3 (491 nm) and film #4 (476 nm)\u0026nbsp;\u003c/p\u003e","description":"","filename":"Fig7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1554124/v1/6ce1d774efa06d9bccca1038.jpg"},{"id":20572328,"identity":"23b9cfbf-f25d-4891-b970-a27a06128ef2","added_by":"auto","created_at":"2022-04-20 19:08:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":781700,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1554124/v1/d4997b91-81cd-4227-a8ca-30423657e069.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eOptical and fractal properties of sputter deposited TiO\u003csub\u003e2\u003c/sub\u003e films\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThin films have unique properties that are significantly different from their corresponding properties in the bulk state. This difference is often due to their physical dimensions (surface to volume ratio), geometric shape, and microstructure. However, a thin film with leveraged characteristics can be synthesized by modifying its properties to a great extent, which is the basis for developing thin film applications in various industries [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Submicron thin films are widely used in Micro-Electro-Mechanical Systems (MEMS), microelectronic integrated circuits, and semiconductors, as well as optical, magnetic, and quantum interference devices. On the other hand, thin films with a large surface-to-volume ratio are used in solar cells for photovoltaic conversion, shielding layers, inactivation layers, etc. Therefore, it is expected that the application of thin films will extend even further by developing many products in the form of a thin film in the near future.\u003c/p\u003e \u003cp\u003eThere are different methods for the mass and easy production of thin films and nanostructures. The differences between these methods are mainly in the mechanism of material transfer from source to the substrate, transfer medium, working pressure and deposition sensitivity, and simplicity of work [\u003cspan additionalcitationids=\"CR3 CR4 CR5 CR6 CR7\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In recent years there has been a surge of interest in nanostructured films of metals and their oxides due to their unique mechanical, chemical, optical, and structural properties [\u003cspan additionalcitationids=\"CR10 CR11 CR12 CR13 CR14 CR15\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Meanwhile, titanium and its associated oxides have been reported to be environmentally friendly and cost-effective materials that exhibit good chemical and optical stability, high corrosion resistance in 3.5% NaCl solution, and insolubility in the water [\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Titanium dioxide (TiO\u003csub\u003e2\u003c/sub\u003e), or titania, shows n-type semiconductor properties at room temperature because of the formation of oxygen voids or titanium atoms within the lattice; each of those defects causes the formation of donor type semiconductors [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe TiO\u003csub\u003e2\u003c/sub\u003e exists in nature with three different crystal structures; anatase, rutile, and brookite, where anatase and rutile have a tetragonal structure while brookite has an orthorhombic structure [\u003cspan additionalcitationids=\"CR25 CR26\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Among the three natural mineral phases of titanium dioxide, the rutile is the most stable and dense phase, while the anatase phase is the least dense. The rutile structure is found naturally in volcanic rocks or rocks exposed to high temperatures and pressures. Rutile is more likely to be found in such environmental conditions due to its low molecular volume than the other two structures. Natural rutile contains about 10% iron, a large amount of niobium, and tantalum. In fact, anatase and brookite are polymorphs of rutile formed by the cooling of igneous rocks [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdditionally, metastable anatase and brookite phases can be formed at temperatures above 600\u0026deg;C. The brookite phase is thermodynamically unstable, and it cannot be found independently, though it exists alongside other titanium dioxide phases. The two most commonly used titanium dioxide crystal structures are the rutile and anatase structures. In the rutile structure, the recombination rate of the charges created by light activity is much higher than that of anatase. This causes the low charge transfer of the rutile structure to the reactants and low efficiency, which is the reason to use this material in color compounds. In contrast, the anatase structure with low recombination, high charge transfer, and consequently, high efficiency can be used as a material with suitable optical activity [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTherefore, the application and efficiency of TiO\u003csub\u003e2\u003c/sub\u003e are strongly influenced by its crystal structure, as well as its particle size and shape [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Qiu et al. [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] reported the enhanced photocatalytic efficiency and optical absorption of TiO\u003csub\u003e2\u003c/sub\u003e films through doping with ZrFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e by sol-gel method. When studying the thermal stability of e-beam deposited TiO\u003csub\u003e2\u003c/sub\u003e coatings, it has been shown that the optical loss of coatings synthesized by e-beam deposition decreased with annealing temperature [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Accordingly, great efforts are made to synthesize TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles with controlled size, shape, and porosity to be used in thin films, ceramics, composites, and catalysts [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan additionalcitationids=\"CR33 CR34\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Other applications of TiO\u003csub\u003e2\u003c/sub\u003e include a wide energy gap in all its crystalline forms, a good position of the conduction and valence bands, and chemical stability, which is widely used in photocatalytic and water decomposition applications. Since it has hydrophilic properties, this material can also be used to prepare self-cleaning surfaces [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMoreover, the ability of TiO\u003csub\u003e2\u003c/sub\u003e to absorb ultraviolet light has led to its application in cosmetics, especially sunscreens, to prevent skin damage. Owing to its unique optical and electrical properties, TiO\u003csub\u003e2\u003c/sub\u003e is used in the manufacturing of solar cells, chemical sensors, and optical coatings. It has also been used to extend medical applications such as artificial heart valves and dental implants [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. This substance causes the uniformity of bone cells between medical implants and bone. TiO\u003csub\u003e2\u003c/sub\u003e in solution or suspension can also break down proteins containing the aminoacid proline in places where proline is present [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, no studies have been performed on the effect of working pressure on the surface morphology of thin films by the multifractal method and its relationship with the optical energy gap. Therefore, the present study is primarily based on atomic force microscopy (AFM) measurements of magnetron sputtered TiO\u003csub\u003e2\u003c/sub\u003e films. We utilized AFM and spectrophotometer measurements to study the effect of inward gas flux changes on the structural, morphological, and optical properties of the TiO\u003csub\u003e2\u003c/sub\u003e films. Furthermore, optical data and the Tauc ́s method were used to calculate the energy gap of deposited films.\u003c/p\u003e"},{"header":"2. Materials And Methods","content":"\u003cp\u003eA DC magnetron sputtering system with a cylindrical glass chamber was used to deposit TiO\u003csub\u003e2\u003c/sub\u003e films. The chamber consisted of two electrodes facing each other, one at the bottom with a larger radius (location under the films) and the other at the top with a radius of 9 cm connected to the DC source. A schematic of the deposition chamber is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Glass and silicon substrates were first cleaned in soap solution and then in an ultrasonic bath by immersing in acetone for 5 min. Then after drying, the substrate wafers were inserted into the chamber and placed on the grounded electrode. Oxygen and argon gases were introduced into the chamber with a flow rate of 4 sccm and 1 sccm, respectively. A mass flow controller (MFC) was used to adjust the working pressure of the chamber. A pure titanium target was sputtered by applying a constant power of 400 W in the medium of argon and oxygen to reactively deposit titanium oxide thin films. Detailed information on deposition parameters is listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\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\u003eThe process parameters for fabricating the films.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e film\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eSputtering parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eThickness (nm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eBase pressure (Torr)\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eWorking pressure (Torr)\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ePower density (W/cm\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e#1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e6.0\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e481\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e#2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e8.0\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e499\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e#3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e1.0\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e491\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e#4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e1.2\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e478\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\u003eIn order to statistically study the surface topography and roughness of the deposited films, an atomic force microscope (NT-MDT model BL022) in non-contact mode was used. The measurements were conducted on the 5\u0026times;5 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e area of the films. Using the spectrophotometer (Hitachi, model U-3501), the transparency spectra of the films were measured in the range of 300 nm to 900 nm. Subsequently, using this data, the absorption spectra of the films were drawn, then the energy gap was calculated using the Tauc ́s method [39] as follows;\u003c/p\u003e \u003cp\u003eWhen a light beam enters a matter, the intensity of the output light is expressed by Beer-Lambert law, as follows;\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$I={I}_{0}{e}^{-\\alpha d}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cem\u003eI\u003c/em\u003e is the intensity of the transmitted light, \u003cem\u003eI\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e is the intensity of the incident light, \u003cem\u003ed\u003c/em\u003e is the thickness of the layer, and \u003cem\u003eα\u003c/em\u003e is the linear absorption coefficient of the material. From the above equation, the absorption coefficient can be calculated, which is used to obtain the energy gap in the Tauc ́s method.\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\alpha =\\frac{1}{d}Ln\\left(\\frac{1}{T}\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe \u003cem\u003eT\u003c/em\u003e here is the transmittance which is defined as the fraction of transmitted intensity to incident intensity. The relationship between the absorption coefficient and the photon energy is expressed as follows:\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$${\\left(\\alpha h\\nu \\right)}^{n}=A\\left(h\\nu -{E}_{g}\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({E}_{g}\\)\u003c/span\u003e\u003c/span\u003e is the energy gap of matter, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(h\\nu\\)\u003c/span\u003e\u003c/span\u003e is the photon energy, and \u003cem\u003eA\u003c/em\u003e and \u003cem\u003en\u003c/em\u003e are constant coefficients. It is \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 for indirect transitions and \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.5 for direct circuits. By plotting the variation curve \u003cem\u003en (\u003c/em\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\alpha h\\nu\\)\u003c/span\u003e\u003c/span\u003e\u003cem\u003e)\u003c/em\u003e in terms of \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(h\\nu\\)\u003c/span\u003e\u003c/span\u003e and fitting the straight line in the linear range up to \u003cem\u003e(\u003c/em\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\alpha h\\nu\\)\u003c/span\u003e\u003c/span\u003e\u003cem\u003e)\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0, the energy gap value can be estimated.\u003c/p\u003e"},{"header":"3. Results And Discussion","content":"\u003cp\u003eThe surface features strongly influence the optical transmission and absorption processes and explain their behavior in the wide interval of wavelengths. On the other hand, the TiO\u003csub\u003e2\u003c/sub\u003e energy gap value substantially affects the optical processes for higher energies of photons (for wavelengths below 200 nm). The combination of multifractal analysis, as well as optical transmission and absorption processes, provides valuable information to explain the importance of optical processes in the growth of TiO\u003csub\u003e2\u003c/sub\u003e layers.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e shows the AFM images of titanium dioxide films recorded at a 5\u0026times;5 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e scale. The AFM images show that the TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles were formed, and the growth of the layers followed the island growth model (Volmer\u0026ndash;Weber). It can be seen that by increasing the input flux, the particle size distribution was changed, leading to changes in the surface roughness. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e shows the particle size distribution diagram. We know that as the working pressure increases, the density of the plasma on the substrate surface increases, which in turn increases the rate of nucleation and the rate of growth of the nuclei. At the same deposition time, increasing the nucleation rate resulted in an increase in the thickness of the layers, which was confirmed by the thickness measurement results reported by the quartz crystal. When the working pressure was 6\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr, the average particle size was measured to be 52 nm while with increasing the working pressure to 8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e, and then 1.0\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, and finally 1.2\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, the particle size was increased to 58, 60, and 62 nm, respectively. This indicates that the increase in the growth rate of the nuclei leads to a slight increase in the particle size formed in the plasma and accumulated on the surface, which was confirmed by the particle size distribution diagrams obtained from the images.\u003c/p\u003e\n\u003cp\u003eThe roughness values were varied between 1.59 nm and 1.73 nm; as for the lowest pressure, the average roughness was 1.7 nm, while it decreased to 1.65 and then to 1.58 nm with increasing the working pressure. On the other hand, further increasing the working pressure to 1.2\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e led to an increase in the roughness to 1.73 nm. Therefore, no clear relation between the roughness and working pressure was found. However, surface parameters such as maximum height and the total height of roughness profile as well as particle distribution of surface particles might lead to such a result [\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe results of fractal analysis of the TiO\u003csub\u003e2\u003c/sub\u003e films are presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. The multifractal singularity spectra \u003cem\u003ef\u003c/em\u003e(\u0026alpha;) (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(a)) and generalized fractal dimension \u003cem\u003eDq\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(b)) indicate well developed multifractal properties of the \u003cem\u003eh\u003c/em\u003e(\u003cem\u003ex,y\u003c/em\u003e) function determined from the AFM images for all TiO\u003csub\u003e2\u003c/sub\u003e films. The profile of the \u003cem\u003ef\u003c/em\u003e(\u0026alpha;) function indicates a decreasing trend in the surface fractality (over) with increasing the working pressure from 6\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr to 8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr (film #1 and #2). On the other hand, the surface fractality was increased dramatically by further increasing the working pressure from 8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e to 1.2\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e Torr (films #2 - #4). The width of the \u003cem\u003ef\u003c/em\u003e(\u0026alpha;) function corresponds to a broader range of surface features (see. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(a)). Therefore, comparing the multifractal spectra of deposited TiO\u003csub\u003e2\u003c/sub\u003e films reveals a broadening of \u003cem\u003ef\u003c/em\u003e(\u0026alpha;) with the working pressure above 8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr, which can be attributed to the increasing non-uniformity in the distribution of surface features at higher pressures.\u003c/p\u003e\n\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(a), for the working pressure of 6.0\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr, the left arm of the curve is longer, which indicates that larger nanoparticles were identified on the surface of this layer. However, as the working pressure increased, the curves changed, and the right arm of the curves became taller, indicating that smaller nanoparticles outperformed larger nanoparticles in determining the surface behavior of the layers. As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(b), an identical conclusion can be deduced from the trend of generalized fractal dimension \u003cem\u003eDq\u003c/em\u003e. Here, the slope of the \u003cem\u003eDq\u003c/em\u003e function is associated with the fractality of the surface. Increasing the working pressure from 6\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr to 8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr (films #1 and #2) led to a slight decreasing fractality, while a further increase in the pressure resulted in a significant increase in multifractality (films #2 - #4). These results are in good agreement with the values of (\u0026alpha;\u003csub\u003emax\u003c/sub\u003e-\u0026alpha;\u003csub\u003emin\u003c/sub\u003e) and (\u003cem\u003eDq\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e \u003cem\u003e- Dq\u003c/em\u003e\u003csub\u003e\u003cem\u003emin\u003c/em\u003e\u003c/sub\u003e) in which the minimum was assigned to film #2 (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(c)), whereas, for the higher working pressures above 8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr, an increase in the multifractality was observed. The bigger the value of (\u0026alpha;\u003csub\u003emax\u003c/sub\u003e- \u0026alpha;\u003csub\u003emin\u003c/sub\u003e), the higher the \u003cem\u003eh\u003c/em\u003e(\u003cem\u003ex,y\u003c/em\u003e) fluctuations are expected. The \u003cem\u003eh\u003c/em\u003e(\u003cem\u003ex,y\u003c/em\u003e) fluctuations detected by the multifractal singularity spectra were also the smallest for film #2.\u003c/p\u003e\n\u003cp\u003eAnother technique that was used further to describe the surface morphology of the deposited layers was Minkowski Functionals analysis. Minkowski boundary and Minkowski connectivity curves for all samples were calculated using the Gwyddion software. The curves obtained from the analysis of 4 samples are illustrated in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e. The curves show that the Minkowski boundary and Minkowski connectivity are functions of working pressure. It was observed that the maximum boundary was obtained for sample 2. These results indicate the nanoparticles were placed on the surface so that they have the most boundaries. It is known that the Minkowski connectivity describes the measure of the number of connections in the nanoparticles pattern by analyzing the relationship between connected and disconnected pixels in an image. Also, as can be seen, the minimum and maximum of the Minkowski connectivity curve for sample #2 are higher than others. Therefore, the connection between nanoparticles in sample #2 was dominant, and the high connection occurs for larger nanoparticles at the surface of samples #1 and #2 compared to samples #3 and #4.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e. depicts the transmission and absorption spectra of the TiO\u003csub\u003e2\u003c/sub\u003e films in the visible region, derived from the dominant relationships between the optical spectra (transmission, absorption, and reflection). The films exhibited high absorption edges for wavelengths above 350 nm, which can be confirmed by a shift in their optical spectra (absorption edges) to higher wavelengths by increasing the working pressure. The minimum and maximum transparency in the films were almost constant, about 50% and 90%, respectively. It is notable that the optical behavior of #1 and #4 films, which were prepared at the lowest and highest pressures, respectively, were almost identical, while there was a slight phase shift in the wavelength of films #2 and #3. Therefore, it can be concluded that they exhibited similar transmittance and absorbance. This is in accordance with the changes in the surface roughness obtained from the AFM data.\u003c/p\u003e\n\u003cp\u003eIn a semiconductor material, the dependence of the absorption of the UV-visible radiation can be determined by the electronic transitions between the valence band and the conduction band. Therefore, the optical properties of semiconductors can be modified by controlling the band gap energy. On the other hand, the band gap energy in thin films strongly depends on the surface roughness and correspondingly on the fractal features of the coating.\u003c/p\u003e\n\u003cp\u003eAs discussed above, the Tauc ́s equation was used to determine the magnitude of the bandgap in TiO\u003csub\u003e2\u003c/sub\u003e films. This is possible by analyzing the data in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e, n (ahʋ) in terms of hʋ, and extrapolating the values obtained in the high energy region with the horizontal axis. The closer the value of this parameter to zero, the higher the conductivity; thus, the better the semiconductor or non-conductive properties of the material. The results of this analysis are given in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e. The energy gap of layers was found to be 3.98, 3.95, 4.03, and 4.00 eV for samples #1, #2, #3, and #4, respectively. It is notable that the energy gap of all TiO\u003csub\u003e2\u003c/sub\u003e films was in the vicinity of 4.00 eV, while the slight variation can be attributed to the changes in the working pressure. The results show that the lowest energy gap is related to the layer with the lowest ∆\u0026alpha;, indicating that the surface complexity affected the energy gap.\u003c/p\u003e\n\u003cp\u003eAs we know, several factors can influence the energy gap of semiconductors. For instance, the energy gap value strongly depends on the crystal structure (such as defects, charged impurities, disorder at the grain boundaries), morphology (such as roughness, fractality, particles shape, and particles quantum size), the thickness of layers, and chemical composition of the material. Here, our aim was to study the effect of the surface morphology of the films on their energy gap. The results showed that increasing the multifractality of the films increased their energy gap. The high energy gap of the deposited layers can be ascribed to the multifractal properties of their surface, the small nanoparticle size (see particle size distribution diagram in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eThe energy gap determined by the Tauc ́s method is not very sensitive to changes in working pressure, as the \u003cem\u003eEg\u003c/em\u003e value is influenced mainly by material properties. The high absorption of wavelengths under 200 nm can be observed in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(b) for all structures, which was closely related to \u003cem\u003eEg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;4 eV determined by the Tauc ́s method for the TiO\u003csub\u003e2\u003c/sub\u003e layers. The development of surface features shows significant sensitivity of multifractal behavior on working pressure (see Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(c and d). The modification of surface features by applied forming steps (revealed by multifractal methods) directly influenced the spectral transmission and absorption processes. The shifts of spectral transmittance (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(a)) and absorbance (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(b)) curves directly correlated with the trends of multifractal parameters determined from the AFM \u003cem\u003eh\u003c/em\u003e(\u003cem\u003ex\u003c/em\u003e,\u003cem\u003ey\u003c/em\u003e) functions. The multifractal analysis provides valuable information about the surface properties and can directly explain the spectral absorption and transmission processes.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this research, titanium dioxide films were deposited at different working pressures utilizing a magnetron sputtering system. The surface morphology and optical properties of TiO\u003csub\u003e2\u003c/sub\u003e films were investigated. According to the measurement of the crystal thickness gauge installed on the device, it was shown that the thickness of the TiO\u003csub\u003e2\u003c/sub\u003e films was varied with the pressure where the optimum pressure of 8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr was found for film #2 with the maximum thickness. Also, multifractal properties synergistically interacted with the development of the thickness of the films during the deposition. Investigation of AFM results revealed that particle size was changed with the pressure leading to the changes in the surface roughness and fractality of the films. Additionally, the nonuniformity in the distribution of surface properties and multifractality increased by raising working pressures.\u003c/p\u003e\n\u003cp\u003eThe changes in the thickness of the films were also evident in the optical spectra, wherein film #2 exhibited the lowest transmission while films #1 and #4 showed the highest transmission values. Also, it was found that by increasing the working pressure, absorption edges shift to higher wavelengths and possess high values for wavelengths greater than 350 nm. The energy gap and minimum and maximum transparency of the TiO\u003csub\u003e2\u003c/sub\u003e layers were less sensitive to changes in the working pressure. Using the Tauc ́s method, the energy gap of the films was calculated to be ~\u0026thinsp;4eV. Such a large energy gap can be attributed to the small grain size of TiO\u003csub\u003e2\u003c/sub\u003e coatings. Eventually, the obtained results from the multifractal analysis showed that at the working pressure of 8.0\u0026times;10\u003csup\u003e\u0026minus;3\u003c/sup\u003e Torr, the layers have the lowest ∆\u0026alpha; and, therefore, the least complexity, as well as the lowest energy band gap.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe acknowledge the financial support of the Ministry of Industry and Trade of the Czech Republic, grant no. FV40238.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDisclosure statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo potential conflict of interest was reported by the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCredit author statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eR. Sh.\u0026nbsp;\u003c/strong\u003e\u0026amp; \u003cstrong\u003eE.\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eN.\u003c/strong\u003e\u003cstrong\u003e:\u003c/strong\u003e Conceptualization and analyses; \u003cstrong\u003eA. A,\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eS. J\u003c/strong\u003e,\u003cstrong\u003e\u0026nbsp;B. A\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eStereometric, fractal Methodology, writing, and editing; \u003cstrong\u003eM. M:\u003c/strong\u003e Investigation and editing; \u003cstrong\u003eGh. A.:\u003c/strong\u003e optical measurements; \u003cstrong\u003eS. M.:\u003c/strong\u003e Resources, review and editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMirzaei, S., Alishahi, M., Souček, P., Žen\u0026iacute;šek, J., Holec, D., Koutn\u0026aacute;, N., Burš\u0026iacute;kov\u0026aacute;, V., Stupavsk\u0026aacute;, M., Z\u0026aacute;bransk\u0026yacute;, L., Burmeister, F., Blug, B., Czig\u0026aacute;ny, Z., Bal\u0026aacute;zsi, K., Mikšov\u0026aacute;, R., Vašina, P.: The effect of chemical composition on the structure, chemistry and mechanical properties of magnetron sputtered W-B-C coatings: Modeling and experiments. Surf. Coat. Technol. \u003cb\u003e383\u003c/b\u003e, 125274 (2020)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDas, A., Chawla, V., Matos, R.S., Filho, H.D. da Yadav, F., P, R., Ţălu, Ş, Kumar, S.: urface microtexture and wettability analysis of Quasi Two-Dimensional (Ti, Al) N thin films using Fractal Geometry. \u003cem\u003eSurf. Coat. 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Eng. \u003cb\u003e33\u003c/b\u003e(10), 779\u0026ndash;786 (2017)\u003c/span\u003e\u003c/li\u003e\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":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"optical-and-quantum-electronics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"oqel","sideBox":"Learn more about [Optical and Quantum Electronics](https://www.springer.com/journal/11082)","snPcode":"11082","submissionUrl":"https://submission.nature.com/new-submission/11082/3","title":"Optical and Quantum Electronics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"TiO2, Magnetron sputtering, Optical properties, AFM, Fractal analysis","lastPublishedDoi":"10.21203/rs.3.rs-1554124/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1554124/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, TiO\u003csub\u003e2\u003c/sub\u003e films were deposited on the glass and silicon substrates at different pressures using a DC magnetron sputtering system. Surface topography, fractality, particle size, transparency spectra, and roughness of the deposited films were analyzed through atomic force microscopy (AFM) in non-contact mode and spectrophotometer (UV-visible) analysis. The surface morphology, absorption spectra, transparency, and conductivity of the films were studied through analytical and mathematical relations, including fractal and multifractal dimensions of the films. The pressure influenced the particle size leading to the changes in the surface roughness and fractality of the films. When the working pressure increased above 8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Torr, the nonuniformity in the distribution of surface properties and multifractality increased. Additionally, using optical data and the Tauc ́s method, their energy gap was calculated. It was revealed that the TiO\u003csub\u003e2\u003c/sub\u003e coatings have a relatively large energy gap of ~\u0026thinsp;4eV, probably due to their small grain size.\u003c/p\u003e","manuscriptTitle":"Optical and fractal properties of sputter deposited TiO2 films","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-04-20 18:58:34","doi":"10.21203/rs.3.rs-1554124/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2022-04-19T19:30:29+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2022-04-18T16:58:45+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Optical and Quantum Electronics","date":"2022-04-15T11:19:21+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2022-04-15T06:44:04+00:00","index":"","fulltext":""},{"type":"submitted","content":"Optical and Quantum Electronics","date":"2022-04-13T07:46:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"optical-and-quantum-electronics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"oqel","sideBox":"Learn more about [Optical and Quantum Electronics](https://www.springer.com/journal/11082)","snPcode":"11082","submissionUrl":"https://submission.nature.com/new-submission/11082/3","title":"Optical and Quantum Electronics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"209bb09e-19e3-460e-bec3-84e6c0a9e7d4","owner":[],"postedDate":"April 20th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2022-10-07T15:13:59+00:00","versionOfRecord":[],"versionCreatedAt":"2022-04-20 18:58:34","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1554124","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1554124","identity":"rs-1554124","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}