NO2 sensitivity of wide area SiC and epitaxial graphene on SiC substrates

摘要

SiC has cemented its place as a material of choice for high power devices that can operate at high temperature and harsh environment due to its high critical breakdown field (> 2 MV/cm), high thermal conductivity (120 W/m-K), and high electron saturation velocity. Therefore, SiC is one of the commonly materials used in high temperature gas sensors in catalytic converter today. Most SiC gas sensors are in the form of schottky diodes or capacitive MIS devices [1] where target molecules would dissociate on the catalyst metal surface and create a change in potential barrier across the interface. Despite its widespread application in high temperature gas sensors, SiC is still used as substrate material as gaseous adsorption on thin film semiconductor surfaces does not change the conductance of the overall film significantly. Consequently, research reports on molecular adsorption on SiC thin films and related electronic property changes are scarce. Nevertheless, theoretical calculations involving SiC nanotubes show that they can bind gaseous molecules [2] and also reports on experimental evidences of H2 detection utilizing resistance change of 3C-SiC thin films [3] are present. In this work, microcantilever based electrostatic force microscopy is applied to find out the surface work function (SWF) changes of wide area SiC thin films with the adsorption of NO2 molecules. Any sensitivity variation between Si and C faces of SiC and also between undoped and doped SiC is also discussed.