Preparation And Properties Of V₂O₅ Thin Films Derived By Sol-Gel Process

Recently, among the transition metal oxide semiconductors, vanadium pentoxide (V₂O₅), especially in thin film form, has attracted considerable interest due to his remarkable electrics, optics and physical chemistry properties and his unique structure. So, it is important to study the preparations, properties and application of V₂O₅ thin films.In this paper, we report the synthesis, microstructure and optical property studies of vanadium pentoxide. The main points are summarized as follows:1. Through sol-gel method with spin-on technology, we deposited V₂O₅ thin film. The problem of bonding between vanadium pentoxide thin film and substrate is settled via studying the mechanism of hydrophilic treatment on silicon substrate surface.2. The composition, phases and morphology of samples with different substrates which were treated at different temperatures were characterized by X-ray diffraction, scan electron microscopy. The results indicated that the samples were amorphous before annealing, and the surface morphology were crack-free, compact and smoother on glass substrate. Highly orientated <001> V₂O₅ thin films which were compose of different particles with different substrates was formed after annealing at 500°C. It showed that V₂O₅ thin films were grew along c axis and yielded to crystalline perovskite structure. The FT-IR and Raman analysis indicate that all vibrational modes change remarkably after the removal of water molecules from V₂O₅ interlayer, which shows that V-O-V band is involved in the redox reaction. The stretching vibration of V=O shifts to higher wavenumbers, which can be explained by a banding vanishing between H₂O and the V₂O₅ framework, most likely via H₂O…O=V bonds. V₂O₅ thin films were more provided with layer microstructure from point of spectroscopy view.3. The results of measurement about V₂O₅ film's UV-Vis transmission spectra and refraction index under different annealing temperature indicated that the optical absorption spectra of all the samples exhibited two distinct regions of behavior. Consequentially the optical properties of the thin films changed greatly with increase of annealing temperature. The absorption in the near-ultraviolet region increased drastically in the case of annealing temperature rising. The optical band gap (E_g) was found to become narrower as annealing temperature increased.