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In this work, TiO2 nanotube thin ¯lms were prepared by using the anodization technique. Di®erent electrolytes solutions were used to specify the optimum condition. Annealing in air at di®erent temperatures of (400, 500, and 600)C at constant time of 1 h was achieved for all ¯lms. The structure (XRD, SEM, EDX, and AFM), and optical (UV–Visible spectroscopy, PL spectroscopy, and Spectral Response) properties of nanotube TiO2 ¯lms were investigated and analyzed for different electrolyte solutions. XRD analysis of all deposited ¯lms has con¯rmed the formation of polycrystalline-tetragonal phase (anatase, and rutile) with increase in crystalline size and, annealing temperatures. SEM measurements of TiO2 ¯lms show nanotube shapes with outer diameter of (80– 130) nm. EDX analysis con¯rmed the stoichiometry ratio between Ti and O to be 1:2 to produce TiO2 ¯lm. PL measurement results show two peaks: one located at UV-region pointing to energy band gap (Eg) for TiO2 nano ¯lms; the second one is located at visible region pointing to impurities on ¯lms. Spectral response measurements show photocurrent peaks centered at UV-region (355 nm). Then, TiO2 ¯lms were deposited with di®erent electrolyte solution for photoelectrocatalytic (PEC) application. The higher response to UV-light was received by using TiO2 ¯lm grown by anodization technique with (HNO3 þHF) electrolyte solution. Pure nanocrystalline SnO2 ¯lms were grown on a clean glass substrate by using sol–gel dip coating and chemical bath deposition (CBD) techniques for gas sensor applications. The ¯lms were annealed in air at 300C, 400C, and 500C for 60 min. The deposited ¯lms with a thickness of approximately 300 20 nm were analyzed through X-ray di®raction, scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical absorption spectroscopy. Results revealed that the ¯lms produced by dip coating exhibited a tetragonal rutile structure and those produced by CBD showed a tetragonal rutile and orthorhombic structure. The crystalline sizes of the ¯lms produced by dip coating annealed at 300C, 400C, and 500C were 8, 14, and 22.34 nm and those for CBD ¯lms at these temperatures were 10, 15, and 22 nm, respectively. AFM and SEM results indicated that the average grain size increased as annealing temperature increased. The transmittance and absorbance spectra were then recorded at wavelengths ranging from 300nm to 1000 nm. The ¯lms produced by both the methods yielded high transmission at visible regions. The optical band gap energy of dipcoated ¯lms also increased as annealing temperature increased. In particular, their optical band gap energies were 3.5, 3.75, and 3.87 eV at 300C, 400C, and 500C, respectively. By comparison, the energy band gap of CBD-prepared ¯lms decreased as annealing temperature increased, and their corresponding band gaps were 3.95, 3.85, and 3.8 eV at the speci¯ed annealing temperatures. The ¯lms were further investigated in terms of their sensing abilities for carbon monoxide (CO) gas at 50 ppm by measuring their sensitivity to this gas at di®erent times and temperatures. Our results demonstrated that dip-coated and CBD-prepared ¯lms were highly sensitive to CO at 200C and 250C, respectively.
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Pure nanocrystalline SnO2 ¯lms were grown on a clean glass substrate by using sol–gel dip coating and chemical bath deposition (CBD) techniques for gas sensor applications. The ¯lms were annealed in air at 300C, 400C, and 500C for 60 min. The deposited ¯lms with a thickness of approximately 300 20 nm were analyzed through X-ray di®raction, scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical absorption spectroscopy. Results revealed that the ¯lms produced by dip coating exhibited a tetragonal rutile structure and those produced by CBD showed a tetragonal rutile and orthorhombic structure. The crystalline sizes of the ¯lms produced by dip coating annealed at 300C, 400C, and 500C were 8, 14, and 22.34 nm and those for CBD ¯lms at these temperatures were 10, 15, and 22 nm, respectively. AFM and SEM results indicated that the average grain size increased as annealing temperature increased. The transmittance and absorbance spectra were then recorded at wavelengths ranging from 300nm to 1000 nm. The ¯lms produced by both the methods yielded high transmission at visible regions. The optical band gap energy of dipcoated ¯lms also increased as annealing temperature increased. In particular, their optical band gap energies were 3.5, 3.75, and 3.87 eV at 300C, 400C, and 500C, respectively. By comparison, the energy band gap of CBD-prepared ¯lms decreased as annealing temperature increased, and their corresponding band gaps were 3.95, 3.85, and 3.8 eV at the speci¯ed annealing temperatures. The ¯lms were further investigated in terms of their sensing abilities for carbon monoxide (CO) gas at 50 ppm by measuring their sensitivity to this gas at di®erent times and temperatures. Our results demonstrated that dip-coated and CBD-prepared ¯lms were highly sensitive to CO at 200C and 250C, respectively.
Selma M.H. al-jawad
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This page is a summary of: Preparation of n-ZnO/p-Si solar cells by oxidation of zinc nanoparticles: effect of oxidation temperature on the photovoltaic properties, Applied Physics A, July 2014, Springer Science + Business Media,
DOI: 10.1007/s00339-014-8605-y.
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