TiO2 thin films by chemical vapour deposition: control of the deposition process and film characterisation

Abstract

Uniform TiO₂ thin films on Si(111) wafers have been prepared by means of low-pressure chemical vapour deposition using tetraisopropoxide titanium (TPT) as the precursor. The way in which the deposition process was controlled was found to depend to a considerable extent on temperature. Under TPT pressure of 0.00216 mbar in the reactor, the deposition process was controlled kinetically at temperatures between 325 and 400 °C, while at higher temperatures precursor mass transfer limited the rate of deposition. Kinetic study showed two regions with reaction orders of 1.3 and near-zero (0.14) in TPT, respectively. The film composition, morphology and crystalline structure have been characterised by means of X-ray photoelectron spectroscopy, secondary-ion mass spectrometry, scanning electron microscopy, atomic-force microscopy, X-ray diffraction and Raman spectroscopy. The surfaces of the prepared TiO₂ thin films contained some carbonaceous species, but there was no carbon contamination in the film bulk. Only the anatase phase was observed for all the TiO₂ thin films prepared in the present study. Nevertheless, the orientation of the crystalline structure as well as the film morphology were dependent on the film deposition conditions.