분무열분해법에 의한 TiO2 및 doped-TiO2 박막성장과 물성연구

Abstract

The purpose of this study was to grow TiO2 and doped - TiO2 films and investigate physical properties. TiO2, TiO2:Ca and TiO2:P films were deposited on the glass substrates by spray pyrolysis. Structural, morphological, stoichiometric, and optical properties of TiO2, TiO2:Ca and TiO2:P films have been studied using XRD(X-ray diffractometry), SEM(scanning electron microscope), EDS (energy dispersive X-ray spectroscopy), and UV-VIS spectrophoto -meter. The TiO2 films prepared with substrate temperature of 450 ℃ and then post-annealed at the tepmerature of 600 ℃ in air for 2 hours were identified as tetragonal structure of TiO2 films with (101) preferred orientation. The crystal structure of TiO2:Ca and TiO2:P films were the same as that of TiO2 film and the crystallity of the samples increased with increasing the concentration of doped Ca and P. The morphologies of TiO2 films were not nearly changed and the grain density of the samples increased with increasing annealing temperature. The surface morphologies of grains in the TiO2:Ca and TiO2:P films were changed round-shape for rod-shape increasing with the concentration of doped Ca and P. The metal ion ratio of TiO2, TiO2:Ca and TiO2:P films were nearly accorded with that of the spray solution in the error limit of EDS resolution. The optical transmittance of TiO2, TiO2:Ca and TiO2:P films were 70-90 % in the wavelength ranging from 320 nm to 820 nm. The optical transmittance of TiO2:Ca and TiO2:P films were slightly decreased with increasing with the concentration of Ca and P. The optical absorption spectra obtained near the fundamental absorption edges of TiO2:Ca and TiO2:P films slightly shifted into longer wavelength in VIS region with increasing with the concentration of Ca and P. The optical absorption spectra obtained near the fundamental absorption edge showed that these compounds had a direct energy band gaps. The direct energy gaps of TiO2 films (prepared at 450 ℃) and TiO2 films at 293 K (prepared at 450℃ and post-annealed at 600 ℃ in the air for 2 hours) were 3.260 eV and 3.497 eV respectively. The direct energy gaps of TiO2:Ca films increased with up to the concentration of 6.25 wt% and then decreased. The direct energy gaps of TiO2:P films were nearly constant increased with the concentration of P in the samples.