Ethanol gas sensitivity of carbon nanotip arrays/n-Si heterojunctions at room temperature

Carbon nanotip arrays were grown from silicon substrates via direct current magnetron sputtering at room temperature (RT). The simple carbon nanotip arrays/n-Si (C/Si) heterojunctions were used to detect ethanol gas at RT. The results show that the C/Si junctions have high ethanol gas sensitivity, rapid response, and high recovery speed at RT. Upon exposure to ethanol gas (0.64 g/l) at RT, the resistance of the junction decreases by 35% at a given positive voltage of 8 V. Moreover, the interface capacitance of the junction at 5 kHz can increase by about 40% rapidly when exposed to ethanol gas. The phenomena should be attributed to the change in the Fermi level of the carbon film caused by adsorbing electrons from ethanol molecules. The study shows that the C/Si junctions have potential application as ethanol gas sensors.