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Indium tin oxide (ITO) thin film as a gas sensor has a good stability and performance. The purpose of this paper is to compare the effect of depositing different metal layers in various structures on the gas sensing properties of ITO toward ethanol and carbon dioxide.

In this work, the authors have investigated the effect of depositing an ITO layer by Electron Beam Evaporation technique under, on top and in the middle of the metal layers. Surface morphology and the response of the fabricated sensors were compared and the changes in the response of the sensors to ethanol and carbon dioxide gases were studied at various gas concentrations and operating temperatures. The sensing mechanism and result of the other studies were also discussed.

Comparing various sensor structures reported in this study showed that the ITO nanorods which grow over distinct Ag nano-islands in the ITO/Ag structure has the highest response of 420 per cent to ethanol which is 6 times more than the single-layer ITO sensor. Further, gold nanoparticles on ITO nanorods in Au/ITO/Ag structure produce a very complex structure that exhibits the best response of 150 per cent to carbon dioxide which is 6.5 times more than the single-layer ITO sensor. The response and the recovery times were improved also.

Different ITO-metal gas sensor structures were studied and compared toward ethanol and carbon dioxide. Response enhancement and various surface changes through a series of experiments and analysis were discussed and compared to the literature.