SELF-SUSTAINED NO_2 GAS SENSOR OPERATING AT ROOM TEMPERATURES BASED ON SOLAR LIGHT ACTIVATED p-NiO/n-Si DIODE

摘要

NiO is a promising transparent semiconductor material for optoelectronic applications such as light emitting diodes, photodetectors, and solar light activated gas sensors. In this work, p-NiO/n-Si heterojunction diode was fabricated by DC-sputtering and post annealing techniques. The successful formation of a p-n diode was confirmed by the current-voltage (I-V) measurements, where a SiO_2 isolation layer was deposited by plasma enhanced chemical vapor deposition (PE-CVD) to assure the formation of a p-n junction diode. The (I-V) characteristics in dark conditions at room temperature exhibited diode characteristics, while solar light illumination shifts the I-V characteristics to a photovoltaic effect. The sensing properties of the fabricated diode were tested under solar simulated light, without using any other energy sources and at room temperature. The sensor shows a better response toward oxidizing gases (such as oxygen and Nitrogen) in comparison to reducing gases (ethanol). The here reported p-n heterojunction diodes are promising candidates for the development of self-sustained gas sensors that capable of working at room temperature without using any external power sources except solar light.