Room-temperature ethanol sensor based on ZIF-67 modified silicon nanowires with expanded detection range and enhanced moisture resistance

Silicon nanowires (SiNWs) array is considered as a promising gas sensitive material due to its room-temperature response and compatibility of modern semiconductor technology. However, the sensing response of SiNWs-based sensor could be seriously suppressed by the ambient humidity. Moreover, in terms of volatile organic compounds (VOCs) detection, SiNWs is revealed to be poorly sensitive. Ethanol is an important VOCs, and it has an important application in the detection of drunk driving. In this study, we reveal that the decoration of zeolite imidazole frameworks (ZIF-67) on SiNWs will not only improve the gas-sensing performance to ethanol, broaden the range of dynamic detection, but also enhance the humidity resistance at room temperature. The ZIF-67@SiNWs sensor shows enhanced response upon exposure to 0.25-200 ppm ethanol and exhibits a practical capability to sense 250 ppb ethanol at relative humidity of 25% with a response of 25% at room temperature. At high humidity of 65%, the developed ZIF-67@SiNWs sensor still remain a significant response upon exposure to 0.25-200 ppm ethanol. The sensor show a good concentration stability and maintain 95% performance in 30 days. A heterojunction model and calculation of activation energy were proposed to explain the enhanced sensing response. Finally, first principles calculation was carried out to clarify the enhanced moisture resistance. The improved response of ZIF-67 modified silicon devices to VOCs has greatly broadened applications of silicon-based sensing devices in the fields of bio-sensing and disease detection.