Optical response of SrTiO3 thin films grown via a sol-gel-hydrothermal method published by Ural Federal University eISSN 2411-1414 chimicatechnoacta.ru ARTICLE 2023, vol. 10(1), No. 202310108 DOI: 10.15826/chimtech.2023.10.1.08 1 of 6 Optical response of SrTiO3 thin films grown via a sol-gel-hydrothermal method Yulia Eka Putri a * , Tio Putra Wendari a , Restu Aulia Arham a, Melvi Muharmi a, Dedi Satria b , Rahmayeni Rahmayeni a , Diana Vanda Wellia a a: Department of Chemistry, Faculty of Mathematics and Natural Sciences, Andalas University, Padang 25163, Indonesia b: Department of Pharmacy, Muhammadiyah University of Sumatera Barat, Padang 25172, Indonesia * Corresponding author: yuliaekaputri@sci.unand.ac.id This paper belongs to a Regular Issue. Abstract The polycrystalline SrTiO3 thin films were prepared by the sol-gel-hydro- thermal method on glass substrates. The synthesis pathway was initiated by preparing a clear TiO2 solution using the sol-gel method. This clear solution was then deposited on a glass substrate using the dip coating technique, followed by the transformation of a thin layer of TiO 2 into SrTiO3 by the hydrothermal method. The crystal structure, bond interac- tions, and band gap energy of SrTiO3 thin layers were characterized using X-ray Diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), and UV–Vis Diffuse Reflectance Spectroscopy (UV-DRS). The XRD patterns of all SrTiO3 thin layers indicated the perovskite structure of the samples. The FTIR spectrum showed an interaction of the silanol groups on the surface of the glass substrate with Ti–O–Ti of SrTiO3 layers. The characteristics of the UV-DRS spectrum were influenced by the thickness of the SrTiO3 layer formed on the glass substrate. The findings of this work provide insights for producing SrTiO3 layers with specified thick- ness and morphology. Keywords SrTiO3 thin film perovskite hydrothermal optical properties Received: 18.12.22 Revised: 12.01.23 Accepted: 16.01.23 Available online: 23.01.23 Key findings ● SrTiO3 thin films were synthesized using the sol-gel-hydrothermal method. ● The hydrothermal synthesis time affected the purity of the SrTiO3 thin film. ● The optical bandgap of SrTiO3 was influenced by the specified thickness of the samples. © 2022, the Authors. This article is published in open access under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). 1. Introduction Two-dimensional (2-dimensional/2D) nanomaterials in the form of thin layers have attracted significant attention be- cause of the successful isolation of graphene into sheet forms. Thin films are currently employed in various fields to develop their capabilities [1]. 2D materials have several advantages, such as having layers with a thin atomic-scale arrangement, large surface area, strong mechanical prop- erties, and good electrical and thermal conductivities [2]. This is the main attraction for preparing 2D nanomaterials with good physical and chemical properties and using them in various applications [3]. Metal oxide-based perovskite structures are an im- portant and attractive class because of their wide application range. The strontium titanate (SrTiO3) semi- conductor compound has a typical metal oxide perovskite structure with the Pm3m space group of at room temper- ature. Inside the perovskite structure, Sr2+ ions are in the corners and Ti4+ ions in the centers of the cube, while O2– anions surround Ti4+ ions to form a regular octahedron in the cubic symmetry. Each Sr2+ ion is surrounded by four TiO6 octahedra and coordinated by twelve O2– ions, whereas the Ti4+ ion is sixfold coordinated by the O2– ion [4]. In the TiO6 octahedra, the hybridization of the O-2p state with the Ti-3d state results in a pronounced cova- lent bonding, whereas the Sr2+ and O2– ions exhibit ionic bonding characteristics. Therefore, SrTiO3 has mixed ionic-covalent bonding properties [5]. This type of chem- ical bonding leads to a unique structure, which can be a http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.08 mailto:yuliaekaputri@sci.unand.ac.id http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0003-2610-3780 https://orcid.org/0000-0002-3600-0905 http://orcid.org/0000-0002-5568-8426 http://orcid.org/0000-0003-2569-9914 http://orcid.org/0000-0002-8694-1308 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.08&domain=pdf&date_stamp=2023-01-23 Chimica Techno Acta 2023, vol. 10(1), No. 202310108 ARTICLE 2 of 6 DOI: 10.15826/chimtech.2023.10.1.08 model for electronic materials. In an ideal SrTiO 3 perov- skite structure, there is a flexible ionic arrangement making it easy to modify. So, the structural instability creates new properties and improves the optical and electrical properties [6]. SrTiO3 thin films are amongthe perovskite oxides with various advantages, including catalytic activities [7], elec- trical and dielectric properties [8], ferroelectric proper- ties [9], and a possibility of using them as lattice-matched substrates for high-Tc oxide superconductors [10]. One of the strategies to improve its promising properties is the thin film fabrication techniques. Several thin film growth technique have been reported, such as sputtering [11], sol- gel [12], pulsed laser ablation [13], and chemical vapor deposition [14]. On the other hand, substrate selection is crucial because the substrate greatly affects the quality of the film. Glass, fluorine-doped tin oxide (FTO), indium- doped tin oxide (ITO), silicon, and metal substrates have been used to fabricate SrTiO3 thin films [15]. This work adopted a two-stage sol-gel-hydrothermal technique to deposit SrTiO3 thin films on the glass sub- strate. The first stage was depositing a TiO2 layer on a glass substrate. Then the second stage was the conversion of the TiO2 thin film into SrTiO3 on the same substrate. Synthesis of TiO2 was performed by the sol-gel method. TiO2 was deposited on the glass substrate by the dip coat- ing method. Afterward, the SrTiO3 layer was formed by the hydrothermal method. In forming SrTiO3 thin films using the hydrothermal method, the effect of Sr(OH)2·8H2O con- centration on the structure and the optical response was identified by varying the concentration of Sr(OH)2·8H2O precursor solution. Then, X-Ray Diffraction (XRD) was utilized to analyze the structure and crystallinity of the synthesized sample. Difuse-Reflectance Ultra Violet Visi- ble (DRS UV-Vis) and Fourier Transform Infra-Red (FTIR) spectroscopy methods were also employed to determine optical properties by calculating band gap values and the interaction between the synthesized compound and the glass substrate, respectively. 2. Materials and method 2.1. Chemicals The materials used in this study were titanium tetrachlo- ride (TiCl4) (Sigma-Aldrich 0.09 M in 20% HCl), ammo- nium hydroxide (NH4OH) (Pudac Scientific 25%), hydrogen peroxide (H2O2) (Merck 30%), distilled water, ethanol (C2H5OH) (Merck ≥ 97.5%), silver nitrate (AgNO3) (Sigma- Aldrich), strontium hydroxide octahydrate (Sr(OH)2·8H2O) (Sigma-Aldrich), ice cube, and commercially available glass substrates (76.2 mm × 25.4 mm × 1 mm). 2.2. Instrumentation The tools used in this study were glassware, analytical scales, pipettes, stirring rods, spatulas, pH paper, ice baths, magnetic stirrer (IKA C-MAG HS 7), oven, autoclaves, Teflon vessel, XRD diffractometer PANalytical X'pert PRO, DRS UV- Vis spectrometer Specord 210 Plus Analytic Jena, and FTIR (Fourier Transform Infra-Red spectrometer) Shimadzu-IR Prestige 21. 2.3. Synthesis of TiO2 gel precursor The TiO2 gel precursor solution was synthesized by drop- wise addition of 36 mL TiCl4 into 300 mL of distilled water in an ice water bath while stirring using a magnetic stirrer for 30 min. Then, the 25% NH4OH solution was added drop- wise to adjust the pH of the solution to 7 under stirring for 24 h. The solution was then centrifuged to separate the pre- cipitate and filtrate. The resulting precipitate was washed using distilled water until no Cl– ions remained. The pres- ence of Cl– ions remaining in the solution was detected by adding AgNO3 solution to the remaining washing water un- til no white precipitate of AgCl was formed. 80 mL of dis- tilled water and 28 mL of H2O2 were added to the white free of Cl– precipitate dropwise while stirring using a magnetic stirrer. The mixed solution was then stirred for 4 h until a transparent yellow solution was formed. The color was be- cause of the TiO2 gel precursor [16]. 2.4. Deposition of TiO2 thin films on glass substrate The used glass substrate was commercial glass with the size of 76.2 mm × 25.4 mm × 1 mm. 4 preparatory glass sheets were cleaned using the ultrasonication method in distilled water, acetone, isopropanol, and ethanol, for 15 min in each. The clean glass was dried at room temperature. Then, the TiO2 layer was deposited on the glass substrate using the dip coating method. The glass substrate was dipped for 30 s into the TiO2 gel precursor and then withdrawn with a withdrawal speed of 0.1 cm/s. Afterward, it was dried for 5 min at 100 °C. This procedure was repeated 5 times to achieve several nanolayers of TiO2. After that, the TiO2-coated glass substrate was further dried for 1 h at 120 °C and labeled TOFT. Next, a sheet of TOFT sample was calcined at 500 °C and cooled by normal cooling for 1 h to ensure the formation of TiO2 on the glass substrate. This calcined TOFT sample was labeled TOFK. 2.5. Transformation of TiO2 thin films into SrTiO3 thin films The transformation of the TiO2 thin layer sample into SrTiO3 was conducted by preparing a strontium solution, Sr(OH)2·8H2O, with varying concentrations of 25 mM, 50 mM, and 75 mM. Then, the solution was placed into the autoclave Teflon vessel; the glass substrate coated with TiO2 thin films was placed in a vertical position. The hydrothermal process was conducted at 150 °C for 3 h. After the hydrothermal process was completed, the thin film on the glass substrate was removed from the auto- clave and calcined at 600 °C for 30 min. The synthesized SrTiO3 thin films were labeled STOF-25, STOF-50, and STOF-75. https://doi.org/10.15826/chimtech.2023.10.1.08 Chimica Techno Acta 2023, vol. 10(1), No. 202310108 ARTICLE 3 of 6 DOI: 10.15826/chimtech.2023.10.1.08 3. Results and Discussion The SrTiO3 thin films were synthesized in-situ using two methods. Firstly, the TiO2 precursors were synthesized us- ing the sol-gel method and then deposited on a glass sub- strate using the dip-coating method. Secondly, the SrTiO3 thin films were synthesized using the hydrothermal method through the diffusion of Sr2+ on the TiO2 layer. The resulting SrTiO3 thin film product is a layer that grows evenly on the substrate with good transparency because the color of the glass substrate coated with SrTiO3 is not much different from that of the glass substrate. The differences in the physical shapes of the glass substrate, the TiO2 thin layer, and the SrTiO3 thin layer are shown in Figure 1. This image shows the changes that occurred in the coating process. It can be seen that the glass substrate coated with the TiO2 thin layer still looks transparent (Figure 1b). However, af- ter being coated with SrTiO3, all samples of the SrTiO3 film appear slightly opaque (translucent) (Figure 1d, e, f). The TiO2 layer synthesized by the sol-gel method was in an amorphous form. Therefore, a sintering process was conducted to ensure the formation of crystalline TiO2. TiO2 in the amorphous phase can be altered into a crystalline phase by the sintering process. So, the crystalline TiO2 was characterized by XRD to determine its crystal structure, as shown in Figure 2. The TOFT XRD pattern shows that this thin layer is amorphous because no specific peaks appear. However, the TOFK sample showed diffraction peaks at the 2θ values of 25.2°, 47.8°, and 54.9° indexed as (101), (200), and (105). These diffraction peaks correspond to the ana- tase TiO2 phase based on the ICSD standard No. 9855 [17]. This proves that the thin film TiO2 synthesized by the sol- gel method was successfully formed as a TiO2 gel. There- fore, it can be used as a precursor for synthesizing SrTiO3. Furthermore, the SrTiO3 thin layer samples synthesized by the hydrothermal method were characterized by XRD. The diffraction patterns are shown in Figure 3. The XRD patterns show that the STOF-50 and STOF-75 samples exhibited SrTiO3 diffraction peaks. Meanwhile, STOF-25 samples did not show any SrTiO3 diffraction peaks with only SrCO3 dif- fraction peaks as impurities. Figure 1 Physical appearance of glass substrate (a), TiO2 thin film (b), SrTiO3 thin film (c), STOF-25 (d), STOF-50 (e), STOF-75 (f). The absence of SrTiO3 in the STOF-25 is due to the lower concentration of Sr2+ than the amount sufficient for the stoichiometric formation of SrTiO3. Meanwhile, the pres- ence of diffraction peaks in the plane (110) for the STOF-50 and STOF-75 samples indicates that SrTiO3 formed on the surface of the glass substrate. The shift of plane (110) to- wards smaller 2θ can be caused by several factors, such as (1) lattice strain, (2) sintering process at high temperature, and (3) mismatch of thermal expansion between the SrTiO3 compound and the used glass substrate [18]. Also, the emergence of SrCO3 diffraction peaks is due to the possible reaction of the dissolved CO2 in the autoclave with the Sr2+ ions during the synthesis. This is due to the interaction between Sr2+ and the dissolved CO2 in the aque- ous solution. Theoretically, hydrated alkaline earth solu- tions ((SrOH)2·8H2O) have a high solubility in the presence of carbonate ions (CO32–) because the solution is alkaline. 20 30 40 50 60 (b)(1 0 5 ) (2 0 0 ) In te n si ty ( a .u .) 2 () (1 0 1 ) TiO 2 (ICSD-9855) (a) 24 26 Figure 2 XRD patterns of TiO2 thin films before sintering (TOFT) (a) and TiO2 thin films after sintering (TOFK) (b). 20 30 40 50 60 30 33 * . . * * * * * * Std. SrCO 3In te n si ty ( a .u .) 2 () (a) (b) (c) Std. SrTiO 3 * . SrTiO3 SrCO3 Figure 3 XRD pattern of SrTiO3 thin films: STOF-25 (a), STOF-50 (b) and STOF-75 (c). https://doi.org/10.15826/chimtech.2023.10.1.08 Chimica Techno Acta 2023, vol. 10(1), No. 202310108 ARTICLE 4 of 6 DOI: 10.15826/chimtech.2023.10.1.08 Then, water absorption also causes the strontium to be- come more alkaline. So, the Sr2+ ions are likely to combine with OH– ions to form SrOH+ and absorb CO2 in the auto- clave during the hydrothermal process. The absorbed CO2 is then converted to CO32– and reacts with hydrated strontium to form SrCO3 impurities [19]. Functional group analysis using FTIR aims to determine the presence of interactions in the successfully synthesized STOF-50 and STOF-75 samples. Figure 4 shows the FTIR spectrum of the glass substrate and the synthesized sam- ples in the wave number range of 400– 1600 cm–1. The obtained spectra for the glass substrate and the STOF-50 and STOF-75 samples show specific peaks of their functional groups. The FTIR spectrum of the glass sub- strate showed the presence of the Si–O stretching vibration of the silanol (Si–OH) group at the wave number of 917 cm–1 [20], and the stretching vibration of Si–O in the siloxane (Si–O–Si) group at the wave number of 766 cm–1 [21]. The silanol stretching vibrations were also observed in the spec- trum of STOF-50 and STOF-75 samples; however, these peaks shifted to the wavenumber of 903 cm–1 (STOF-50) and 892 cm–1 (STOF-75). The shift in the wave number of silanol functional groups is due to the strong interaction be- tween the surface of the glass substrate through the silanol present in the surface glass with Ti–O–Ti present in the SrTiO3 compound. The intense interaction results in the for- mation of new chemical bonds through the terminal groups Si–O–H with Ti–O–Ti to produce Si–O–Ti along the surface of the glass substrate and SrTiO3 film. The formation of Si– O–Ti is further strengthened by changes in the intensity of the FTIR spectrum by weakening the silanol peaks in STOF- 50 samples and STOF-75, indicating a stronger Si–O–Ti bond. Furthermore, the appearance of a new peak at a wavenumber of 478 cm–1 in the STOF-50 and STOF-75 spec- trum refers to the Ti–O stretching vibration of the Ti–O–Ti of TiO6 octahedral in the SrTiO3 compound [22]. 1600 1400 1200 1000 800 600 400 500 400 T i- O (b) T r a n sm it ta n c e ( % ) Wavenumber (cm -1 ) (a) (c) S i- O -S i S i- O T i- O Figure 4 FTIR spectrum of glass substrate (a), STOF-50 (b) and STOF-75 (c). DRS UV-Vis analysis was performed to analyze the opti- cal properties of the STOF-50 and STOF-75 samples based on the band gap energy values, as shown in Figure 5a. Both samples demonstrate a good absorbance in UV light at around 325 nm and a weak absorbance in visible light. The STOF-75 sample shows a higher peak intensity than the STOF-50 sample. These results show that the absorbance value is directly proportional to the SrTiO3 concentration on the glass substrate, as the absorbance of the STOF-75 is greater than that of STOF-50 [23]. The obtained band gap for each sample was calculated using the Tauc-Mott (MT) method from the UV-DRS absorption spectrum, according to the following equation: (𝛼h𝑣)2 = A(h𝑣 − 𝐸𝑔), (1) where A is the side width parameter, 𝛼 is the absorption coefficient, h is Plank's constant (J·s), and Eg is the bandgap energy (eV). Figure 5b shows the optical band gap energy of the sam- ples using Tauc plots of the STOF-50 and STOF-75 thin film samples at 2.50 eV and 3.58 eV, respectively. The difference in these values is due to the presence of impurities in the sample, as confirmed by the XRD pattern, and the thickness of the thin layer, known from the absorption of the UV-DRS spectrum. 300 350 400 450 500 0.0 0.2 0.4 0.6 0.8 1.0 1.2 A b so r b a n c e ( a .u .) Wavelength (nm) STOF-75 STOF-50 (a) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 10 20 30 40 50 (b) h (eV) ( h  )2 STOF-75 STOF-50 2.5 eV 3.58 eV Figure 5 UV-Vis spectrum of SrTiO3 thin films (a) and optical band gap energy (b). https://doi.org/10.15826/chimtech.2023.10.1.08 Chimica Techno Acta 2023, vol. 10(1), No. 202310108 ARTICLE 5 of 6 DOI: 10.15826/chimtech.2023.10.1.08 According to the XRD pattern and UV-DRS spectrum, it is known that the STOF-75 sample contains SrCO3 impurities, and its absorption is greater than that of the STOF-50 sam- ple. Therefore, the band gap energy value of the STOF-75 sample is greater than that of the STOF-50 [15]. 4. Limitations In this study, SrTiO3 thin films were not single-phase be- cause SrCO3 was found as an impurity. So, the crystallinity of the samples remained low. Therefore, future research will focus on forming single-phase SrTiO3 thin films by ad- justing several hydrothermal synthesis parameters, such as variations in temperature, time, and the concentration of the starting material. 5. Conclusions SrTiO3 thin films were synthesized using the sol-gel-hydro- thermal method. The concentration of Sr2+ in the solution af- fected the growth of SrTiO3 on a glass substrate, where the STOF-50 and STOF-75 formed a thin layer of SrTiO3. However, the presence of SrTiO3 was not found in the STOF-25 because the strontium solution concentration was insufficient. The FTIR spectrum showed an interaction between the glass sub- strate and SrTiO3 with the appearance of silanol groups. The STOF-50 and STOF-75 samples had a good absorbance in UV light and a very weak absorbance in visible light with band gap values of 2.50 eV and 3.58 eV, respectively. ● Supplementary materials No supplementary materials are available. ● Funding The author would like to thank the Faculty of Mathematics and Natural Sciences, Universitas Andalas, through the PNBP Fund Research Grant No.16/UN.16.03.D/PP/FMIPA/2021. ● Acknowledgments None. ● Author contributions Conceptualization: Y.E.P. Visualization: T.P.W. Investigation: R.A.A., M.M. Methodology: Y.E.P., D.V.W. Supervision: R.R., D.V.W. Writing – original draft: Y.E.P. Writing – review & editing: D.S. ● Conflict of interest The authors declare no conflict of interest. ● Additional information Author IDs: Yulia Eka Putri, Scopus ID 55261197300; Tio Putra Wendari, Scopus ID 57208920083; Dedi Satria, Scopus ID 57200695552; Rahmayeni Rahmayeni, Scopus ID 55544632300; Diana Vanda Wellia, Scopus ID 35363286300. Websites: Andalas University, https://www.unand.ac.id; Muhammadiyah University of Sumatera Barat, https://www.umsb.ac.id. References 1. Britnell L, Ribeiro RM, Eckmann A, Jalil R, Belle BD, Mishchenko A, et al. Strong light-matter interactions in het- erostructures of atomically thin films. Sci. 2013;340(6138):1311–1314. doi:10.1126/science.1235547 2. Das S, Kim M, Lee JW, Choi W. Synthesis, properties, and ap- plications of 2-D materials: a comprehensive review. Crit Rev Solid State Mater Sci. 2014;39(4):231–252. doi:10.1080/10408436.2013.836075 3. Fiori G, Bonaccorso F, Iannaccone G, Palacios T, Neumaier D, Seabaugh A, et al. Electronics based on two-dimensional ma- terials. Nat Nanotechnol. 2014;9(10):768–779. doi:10.1016/j.ceramint.2021.11.075 4. Putri YE, Wendari TP, Rahmah AA, Refinel R, Said SM, Sofyan N, et al. Tuning the morphology of SrTiO3 nanocubes and their enhanced electrical conductivity. Ceram Int. 2022 Feb 15;48(4):5321–6. doi:10.1016/j.ceramint.2021.11.075 5. Trejgis K, Dramićanin MD, Marciniak L. Highly sensitive mul- tiparametric luminescent thermometer for biologically-rele- vant temperatures based on Mn4+, Ln3+ Co-doped SrTiO3 nanocrystals. J Alloys Compd. 2021;875. doi:10.1016/j.jallcom.2021.159973 6. Gastiasoro MN, Ruhman J, Fernandes RM. Superconductivity in dilute SrTiO3: a review. Ann Phys. 2020;417:168107. doi:10.1016/j.aop.2020.168107 7. Riemke FC, Ücker CL, Carreño NLV, da Silva Cava S, Teixeira MP, Fajardo HV, et al. Influence of Nb2O5 grown on SrTiO3 na- noseeds in the catalytic oxidation of thioanisole. Mater Chem Phys. 2022;278:125591. doi:10.1016/j.matchemphys.2021.125591 8. Bhogra A, Masarrat A, Meena R, Hasina D, Bala M, Dong CL, et al. Tuning the electrical and thermoelectric properties of N ion implanted SrTiO3 Thin films and their conduction mecha- nisms. Sci Rep. 2019;9(1):1–11. doi:10.1038/s41598-019-51079-y 9. Song H, Son JY. Examining imprinted ferroelectric hysteresis loops and improved energy storage properties of Mn-doped epitaxial SrTiO3 thin films using heat treatment. Mater Sci Eng B Solid-State Mater Adv Technol. 2022;285:115925. doi:10.1016/j.mseb.2022.115925 10. Ahadi K, Galletti L, Li Y, Salmani-Rezaie S, Wu W, Stemmer S. enhancing superconductivity in SrTiO3 films with strain. Sci Adv. 2019:1–6. doi:10.1126/sciadv.aaw0120 11. Hadj Youssef A, Ambriz Vargas F, Amaechi I, Sarkissian A, Merlen A, Thomas R, et al. Impact of negative oxygen ions on the deposition processes of RF-magnetron sputtered SrTiO3 thin films. Thin Solid Films. 2018;661:23–31. doi:10.1016/j.tsf.2018.05.054 12. Diao C, Li H, Yang Y, Hao H, Yao Z, Liu H. Significantly im- proved energy storage properties of sol-gel derived mn-modi- fied SrTiO3 thin films. Ceram Int. 2019;45(9):11784–11791. doi:10.1016/j.ceramint.2019.03.056 https://doi.org/10.15826/chimtech.2023.10.1.08 https://www.scopus.com/authid/detail.uri?authorId=55261197300 https://www.scopus.com/authid/detail.uri?authorId=57208920083 https://www.scopus.com/authid/detail.uri?authorId=57200695552 https://www.scopus.com/authid/detail.uri?authorId=55544632300 https://www.scopus.com/authid/detail.uri?authorId=35363286300 https://www.unand.ac.id/ https://www.umsb.ac.id/ https://doi.org/10.1126/science.1235547 https://doi.org/10.1080/10408436.2013.836075 https://doi.org/10.1016/j.ceramint.2021.11.075 https://doi.org/10.1016/j.ceramint.2021.11.075 https://doi.org/10.1016/j.jallcom.2021.159973 https://doi.org/10.1016/j.aop.2020.168107 https://doi.org/10.1016/j.matchemphys.2021.125591 https://doi.org/10.1038/s41598-019-51079-y https://doi.org/10.1016/j.mseb.2022.115925 https://doi.org/10.1126/sciadv.aaw0120 https://doi.org/10.1016/j.tsf.2018.05.054 https://doi.org/10.1016/j.ceramint.2019.03.056 Chimica Techno Acta 2023, vol. 10(1), No. 202310108 ARTICLE 6 of 6 DOI: 10.15826/chimtech.2023.10.1.08 13. Jung F, Delmdahl R, Heymann A, Fischer M, Karl H. Surface evolution of crystalline SrTiO3, LaAlO3 and Y3Al5O12 targets during pulsed laser ablation. Appl Phys A Mater Sci Process. 2022;128(9):750. doi:10.1007/s00339-022-05805-5 14. He C, Bu X, Yang S, He P, Ding G, Xie X. Core-shell SrTiO3 /graphene structure by chemical vapor deposition for en- hanced photocatalytic performance. Appl Surf Sci. 2018;436:373–381. doi:10.1016/j.apsusc.2017.12.063 15. Łęcki T, Zarębska K, Sobczak K, Skompska M. Photocatalytic degradation of 4-chlorophenol with the use of FTO/TiO2/SrTiO3 composite prepared by microwave-assisted hydrothermal method. Appl Surf Sci. 2019;470:991–1002. doi:10.1016/j.apsusc.2018.11.200 16. Pratiwi N, Zulhadjri, Arief S, Wellia DV. A facile preparation of transparent ultrahydrophobic glass via TiO2/Octadecyltri- chlorosilane (ODTS) coatings for self-cleaning material. Chem Sel. 2020;5(4):1450–1454. doi:10.1002/slct.201904153 17. Taherniya A, Raoufi D. Thickness dependence of structural, optical and morphological properties of sol-gel derived TiO2 thin film. Nanotechnol. 2018;29(27):1–19. doi:10.1088/2053-1591/aae4d0 18. Zhao J, Deng Y, Wei H, Zheng X, Yu Z, Shao Y, et al. Strained hybrid perovskite thin films and their impact on the intrinsic stability of perovskite solar cells. Sci Adv. 2017;3(11). doi:10.1126/sciadv.aao5616 19. Hong J, Heo SJ, Singh P. Water mediated growth of oriented single crystalline SrCO3 nanorod arrays on strontium com- pounds. Sci Rep. 2021;11(1):1–11. doi:10.1038/s41598-021-82651-0 20. Dimitriadi M, Zafiropoulou M, Zinelis S, Silikas N, Eliades G. Silane reactivity and resin bond strength to lithium disilicate ceramic surfaces. Dent Mater. 2019;35(8):1082–1094. doi:10.1016/j.dental.2019.05.002 21. Aguiar H, Serra J, González P, León B. Structural study of sol- gel silicate glasses by IR and Raman spectroscopies. J Non Cryst Solids. 2009;355(8):475–480. doi:10.1016/j.jnoncrysol.2009.01.010 22. Yao M, Li F, Peng Y, Chen J, Su Z, Yao X. Enhanced electrical characteristics of sol–gel-derived amorphous SrTiO3 films. J Mater Sci Mater Electron. 2017;28(5):4044–4050. doi:10.1007/s10854-016-6018-8 23. Dulian P, Nachit W, Jaglarz J, Zięba P, Kanak J, Żukowski W. Photocatalytic methylene blue degradation on multilayer transparent TiO2 coatings. Opt Mater (Amst). 2019;90:264– 272. doi:10.1016/j.optmat.2019.02.041 https://doi.org/10.15826/chimtech.2023.10.1.08 https://doi.org/10.1007/s00339-022-05805-5 https://doi.org/10.1016/j.apsusc.2017.12.063 https://doi.org/10.1016/j.apsusc.2018.11.200 https://doi.org/10.1002/slct.201904153 https://doi.org/10.1088/2053-1591/aae4d0 https://doi.org/10.1126/sciadv.aao5616 https://doi.org/10.1038/s41598-021-82651-0 https://doi.org/10.1016/j.dental.2019.05.002 https://doi.org/10.1016/j.jnoncrysol.2009.01.010 https://doi.org/10.1007/s10854-016-6018-8 https://doi.org/10.1016/j.optmat.2019.02.041