Selective H2S Gas Sensing With a Graphene/n-Si Schottky Diode

In this investigation, a novel selective gas sensor for detection of H2S gas is proposed based on graphene/n-Si Schottky junction. The sensor's structure is based on a Schottky junction fabricated by mechanical deposition of highly oriented natural graphite on top of an n-type < 100 > silicon substrate. The variation in the forward bias current-voltage characteristics of the diode for different gas concentrations and different temperatures are indications of the gas sensing capability of the proposed sensor. The fabricated graphene-based gas sensor shows good selectivity, reproducibility, and fast response. Considering electrochemical impedance spectroscopy, the sensitivity variation of the sensor in a specific range of frequencies is different for each gas ambient. The response time of about 20 s under the applied voltage of 1 V and 100 ppm of H2S gas ambient is obtained and becomes shorter as the temperature increases. Because of the special structure of the graphene, adsorption, and desorption of the gas occurs fast. Therefore, graphene-based Schottky diodes seem suitable for gas sensing applications.