(Invited) Pure Anatase Phase Titanium Dioxide Thin Films Prepared by Mist Chemical Vapor Deposition Applying for Photocatalysis

Abstract

Up to date, titanium dioxide (TiO2) thin film has attracted considerable interest as the most promising material for a variety of applications and products in the environmental and energy fields, including self-cleaning surfaces, air and water purification systems, and photoelectrochemical conversion because of its outstanding chemical stability and electrical properties, etc [1]. Among the three phases of TiO2, anatase TiO2 has higher photocatalytic activity than rutile and brookite TiO2. Anatase TiO2 films can be synthesized by various methods. However, there were still issues on synthesizing the stable pure anatase phase TiO2 using different methods. Compared with other reported methods, the mist chemical vapor deposition (mist CVD) [2] is an alternative method to synthesize TiO2 thin films, by which the growth of oxide thin film can be precisely controlled according to our previously research [3]. In this research, anatase TiO2 thin films were fabricated on glass by mist CVD method. The precursor solution (150 ml) was prepared by dissolving acetylacetone (0.9 ml) and titanium tetraisopropoxide (TTIP, 0.9 ml) in water and methanol. In order to investigate the temperature on structural, optical and photocatalytic properties of TiO2 films, the deposition temperature were set at room temperature, 200˚C and 400˚C for comparison. During the mist CVD process, mist droplets were generated from the precursor solution by ultrasonic atomization at 2.4 MHz and transferred to the reaction chamber by N2 carrier gas. The structural properties of TiO2 thin films were investigated by X-ray diffraction , Raman spectroscopy and scanning electron microscope, atomic force microscope . The optical properties of TiO2 thin films were investigated by transmittance spectroscopy.According to the morphological analysis, TiO2 films of 300nm with uniform surface were observed from the deposition temperature of 400˚C. There was no thin film at room temperature and some isolated particles observed at 200˚C. Examining the GIXRD patterns of TiO2 films deposited at 400˚C, the following diffraction peaks (101), (004), (200), (211), (201), (204) and (215) were observed, which corresponds to the diffraction peaks of anatase phase TiO2. The transmittance of TiO2 films was higher than 75 % in the visible region. The photocatalytic efficiency of TiO2 film showed the photocatalytic efficiency due to a maximum number of {001} facets and a large surface area.In summary, the pure anatase phase TiO2 thin films could be synthesized at 400˚C by mist CVD method. The obtained anatase TiO2 films showed high photocatocatalytic efficiency. The growth mechanism of pure anatase TiO2 films will be revealed in the paper.References V. Baryshnikova, L. A. Filatov, A.S. Petrov, and S. E. Alexandrov, Chemical Vapor Deposition, 21, 327-333 (2015).Kawaharamura, K. Mori, H. Orita, T. Shirahata, S. Fujita, and T. Hirao, Japanese Journal of Applied Physics, 52, 035501 (2013). Li, C. Li, T. Kawaharamura, D. Wang, N. Nitta, M. Furuta, H. Furuta, and A. Hatta, Transactions of the Materials Research Society of Japan, 39[2], 161-164 (2014).