Influence of substrate temperature on ethanol sensing properties of CdO thin films prepared by facile spray pyrolysis method

Transparent conducting CdO thin films were deposited on to glass substrates by spray pyrolysis technique. The depositions were carried out at different substrate temperatures with varying film thickness. The effects of substrate temperature on structural, optical and electrical properties of CdO thin films were systematically studied. The CdO films were polycrystalline in nature with cubic crystal structure showing preferential orientation along (111) direction. Wettability results confirmed that the hydrophobic character of CdO thin film is enhanced with increase in substrate temperatures. The average transmittance is about 80 %, thus the films are transparent in the visible region. The optical band gap value of the CdO films increased from 2.24 to 2.34 eV with increase in the substrate temperature from 200 to 350 degrees C. Surface morphology studies reveal that the grain size and roughness of the films are increased with increase in the substrate temperature. The minimum value of electrical resistivity of the films is 1.40 x 10(-3) Omega cm obtained at 350 degrees C. The maximum ethanol sensitivity of 33.45 % is observed for the substrate temperature of 300 degrees C. Thus the results authenticate that the substrate temperature influences the structural, optical, electrical and sensing properties of the deposited films.