Effect of Substrates on Structural Properties of Pure Anatase Phase Titanium Dioxide Thin Films Prepared By Mist Chemical Vapor Deposition
Authors: Zhang Qiang , LI Chaoyang 
Published: February 2020

Titanium dioxide (TiO2) thin film has attracted considerable interest as one of promising sensing materials applying for various thin-film gas sensors because of its outstanding sensing properties, chemical stability and electrical properties, etc. [1]. Among the three phases of TiO2 films, anatase phase TiO2 has better sensitivity to H2 and volatile organic compound gases than rutile phase TiO2 [2,3]. 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) [4] 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 [5].

In order to investigate the effect of substrates on structural properties of TiO2 films fabricated by mist CVD method, four kinds of substrates were selected for comparison: glass, quartz glass, gallium doped zinc oxide (GZO) film and p-type silicon. During the mist CVD process, a solution of mixed precursors was prepared by dissolving titanium tetraisopropanolate in ethanol. The mist droplets were generated from the solution by ultrasonic transducer and transferred to the reaction chamber by compressed air. The substrates were set in the reaction chamber, which was heated and kept at 400 ˚C during the deposition. The structural properties of TiO2 thin films were investigated by X-ray diffraction (XRD), 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 with uniform surface were observed on the different substrates. Examining the XRD patterns of TiO2 films, the following diffraction peaks (101), (004), (200), (211), (201), (204) and (215) were observed, which corresponded to the diffraction peaks of anatase phase TiO2. However, it was found that the intensity of dominated (101) peak increased with the order of TiO2 films on quartz glass, GZO, silicon and glass. The results of TiO2 films by Raman spectroscopy measurement were also agreed with that of XRD measurement. In summary, the pure anatase phase TiO2 thin films could be synthesized by mist CVD method. The obtained anatase phase TiO2 films have high potential to be applied to thin film gas sensors, photocatalyst and dye-sensitized solar cells. The growth mechanism of TiO2 films on the different substrates will be revealed in the paper.

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