Influence of annealing temperature on sensing properties of TIOx thin films prepared by magnetron sputtering

Abstract

This work describes the influence of the annealing temperature on the optical and surfaceproperties of non-stoichiometric titanium oxide (TiOx) thin films. The results were related to theinvestigation of the sensing response toward H2 gas. The samples were prepared by the magnetronsputtering method using Ar:O2 plasma with low oxygen content (20% and 30%). An increase in theamount of oxygen in the gas mixture supplied to the magnetron led to a decrease in the deposition rate.The thickness of the deposited thin films, determined by the use of an optical profiler, was found tobe 600 nm and 200 nm, respectively. The coatings were then annealed in an ambient air atmosphereat a temperature in the range from 100C to 800C. Additionally, the roughness of the coating surfacewas measured. To investigate the optical properties of the thin films, transmission and reflection spectrawere measured, and parameters such as transmission coefficient, cutoff wavelength value, and opticalband gap value were determined as functions of the annealing temperature. The sensing propertiesof the thin films were characterised on the basis of changes in a resistance value as a response to amix of Ar:3.5% H2. It was found that the oxidation of the thin films has a key influence not only onthe response time of the TiOx thin films, but also on the character of the response.Keywords: materials engineering, titanium oxides, thin films, magnetron sputtering, optical properties,gas sensing properties