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.