Current–voltage characteristics and ethanol gas sensing properties of ZnO thin film/Si heterojunction at room temperature

The polycrystalline zinc oxide film/p-Si (ZnO/Si) heterojunctions were fabricated by radio-frequency (RF) magnetron sputtering. The current–voltage (I–V) characteristics and ethanol gas sensing properties of the heterojunctions were investigated at room temperature (RT). It is found that the simple ZnO/Si heterojunctions can be used to detect ethanol gas at RT. Upon exposure to 200 ppm ethanol at RT, the heterojunction showed the maximum sensitivity of 67.6% at +7 V bias voltage, which is much better than the results reported before. The phenomena should be attributed to the change of carrier concentration of ZnO film and the change of potential barrier width of the junction, which is caused by the adsorption of ethanol gas molecules. The study shows that the ZnO/Si junctions have potential application as RT ethanol sensors.