Effect of film thickness on liquefied petroleum gas (LPG) sensing properties of SILAR deposited CdO thin films

Nanocrystalline cadmium oxide (CdO) thin films of different thicknesses were deposited on a glass substrate by a simple chemical method (successive ionic layer adsorption and reaction, SILAR) based on alternate dipping of the substrate in an alkaline cadmium nitrate solution and double-distilled water containing 1% H2O2, followed by air heat treatment at 723 K for 5 h. The cadmium oxide thin films were used as sensing layers for liquefied petroleum (LPG) resistive gas sensors. These samples were structurally and morphologically characterized using X-ray diffraction and SEM techniques, respectively. The dependence of LPG sensing properties on the thickness of CdO thin film was investigated. Maximum gas response achieved was 18.75% for the film of thickness 1.5 μm at a fixed gas concentration of 0.08 vol% at 698 K.