Oxygen plasma treated graphene/InN nanowire heterojunction based sensors for toxic gas detection

摘要

In this work, graphene/InN nanowire (NW) heterostructure based diode and field effect transistor devices are studied for potential gas sensing applications. InN NWs were grown on SiO2/Si substrate and CVD grown graphene was then transferred on them to make a graphene/InN diode structure. Some of the NW samples were treated with O2 plasma for various durations of time before transferring graphene, which was believed to have lowered the surface charge concentration and to improve rectifying behavior. Preliminary experiments with trace amount of NO2/NH3 gas down to sub-ppm concentration showed highly promising results. In another experiment, the doped Si substrate was used to form a back gate to modulate the electrical characteristics of the diode and to operate it as a field effect transistor, which also resulted in even lower limit of detection (low ppb). The functionality of these sensors depends on the presence of a tunable Schottky barrier formed between the 1D/2D heterojunction of graphene and InN NW that can be modulated by different analyte gas molecules or external stress.