Effects of Deposition Rate on the Structural, Morphological and Optical Properties of Brookite TiO2 Films Prepared by MOCVD

Compared to anatase and rutile TiO2, the brookite TiO2 (b-TiO2) is relatively seldom investigated, because it is difficult to be prepared. In order to explore a scientific and effective approach to prepare high quality b-TiO2 crystalline films, the effects of deposition rate on the properties of b-TiO2 films prepared on yttria-stabilized zirconia (YSZ) (110) substrates by metal organic chemical vapor deposition (MOCVD) were investigated in this study. The structural analyses indicated that the b-TiO2 film prepared with the lowest deposition rate of 1.25 Å/min had the best single crystalline quality for which the epitaxial relationship between the film and substrate was determined as b-TiO2(120) || YSZ(110) with an in-plane epitaxial relationship of b-TiO2[001]|| YSZ[001] and b-TiO2[20]||YSZ[10]. The RMS surface roughness of the obtained films decreased from 7.02 to 1.11 nm as the deposition rate decreased. The average transmittances of all the obtained b-TiO2 films exceeded 90% in the visible range. The optical band gaps increased from 3.54 to 3.63 eV as the deposition rate decreased. Apparently, the deposition rate has a significant influence on the structural, morphological and optical properties. Therefore, it provides a practicable way to manipulate such properties of b-TiO2 films for different applications in the field of transparent optoelectronic devices.