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

Abstract

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°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 9 10 -3 X cm obtained at 350°C. The maximum ethanol sensitivity of 33.45 % is observed for the substrate temperature of 300°C. Thus the results authenticate that the substrate temperature influences the structural, optical, electrical and sensing properties of the deposited films.

Characterization and NO2 gas sensing performance of CdO:In2O3 polycrystalline thin films prepared by spray pyrolysis technique

“…The negative sign of Hall coefficients for all CdO:In 2 O 3 thin films confirmed the n-type nature conductivity of this system. This is caused due to the existence of defects such as oxygen vacancies and/or intrinsic interstitial cadmium atoms, which can be easily ionized [42,43]. The induced electrons from this process contribute to the conduction of electricity, causing CdO to act as an n-type semiconductor.…”

Chemical spray pyrolysis deposition of transparent and conducting Fe doped CdO thin films for ethanol sensor

“…The most common application of ethanol sensors is as a breath analyser, since the ethanol vapour in human breath is correlated with the concentration in the blood. Recently, gas sensors based on the semiconducting metal-oxides such as SnO 2 , ZnO, CdO, ITO, WO 3 , and CuO have been found to be very useful for detecting ethanol vapour [1][2][3][4][5][6][7][8][9]. It was found that cadmium oxide based thin films having high sensitivity to ethanol gas because of very thin discontinuous layer surface of CdO films can remarkably enhance its gas-sensing characteristics [10,11].…”