Growth of TiO2:Au thin films on Si substrates by Spin coating method

Abstract

Thin titanium dioxide: gold (TiO₂:Au) films are grown on n-type Si(100) substrates by spin coating, using 97% pure titanium (IV) isopropoxide [TTIP, Ti(O(C₃H₇)₄] as a metal-organic precursor and powdered gold oxide (Au₂O₃) as a dopant. The Au₂O₃ was dissolved in tetrahydrofuran (C₄H₈O) to a concentration of 0.2 M, and this was then mixed with the TTIP in a 1:4 ratio. This experiment used a TTIP buffer layer to reduce lattice mismatch between the substrate and the film. The growth temperature was varied from 400°C to 550°C with an interval of 50 °C during deposition of TiO₂:Au films, in which the experimental results show that the grown film exhibited rutile (002) (R (002)) crystal planes for all temperature conditions. In addition, while the films were grown at a temperature of 400 °C and 450 °C showed anatase (211) planes, the layers realized with a temperature of 450°C and 550°C exhibited rutile (200) planes. Increasing the amount of Au incorporation within a film will decrease its bandgap energy. The 500°C films showed a crystalline domain size in the R (002) plane of around 20.38 nm, making it a promising candidate base material for use in carbon monoxide (CO) gas sensors.