Tungsten oxide thin films sputter deposited by the reactive gas pulsing process for the dodecane detection

The DC reactive magnetron sputtering of a metallic tungsten target was performed in an argon + oxygen atmosphere for depositing tungsten oxide thin films. In order to control the oxygen concentration in the films, the reactive gas pulsing process, namely RGPP, was implemented. Rectangular pulses were used with a constant pulsing period T = 16 s whereas the duty cycle alpha (time of oxygen injection to pulsing period T ratio) was systematically changed from 0 to 100 % of T. This pulsing injection of the reactive gas allowed a gradual evolution of the films composition from pure metallic to over-stoichiometric WO3+epsilon' compounds. These WOx films were sputter deposited on commercial MSP 769 Heraeus platforms so as to be used as a sensor for the dodecane gas. It is shown that the sensing performances carried out at 573 K can be adjusted as a function of the duty cycle used during the deposition stage. The relationship between sensing properties and physic-chemical behaviours of the films was especially discussed. (C) 2015 Elsevier Ltd. All rights reserved.