Electric Transport in Few-Layer ReSe(2) Transistors Modulated by Air Pressure and Light

We report the fabrication and optoelectronic characterization of field-effect transistors (FETs) based on few-layer ReSe(2). The devices show n-type conduction due to the Cr contacts that form low Schottky barriers with the ReSe(2) nanosheet. We show that the optoelectronic performance of these FETs is strongly affected by air pressure, and it undergoes a dramatic increase in conductivity when the pressure is lowered below the atmospheric one. Surface-adsorbed oxygen and water molecules are very effective in doping ReSe(2); hence, FETs based on this two-dimensional (2D) semiconductor can be used as an effective air pressure gauge. Finally, we report negative photoconductivity in the ReSe(2) channel that we attribute to a back-gate-dependent trapping of the photo-excited charges.