Optical transitions in monolayer WS2 observed through transient photoconductivity in MIS structures

Abstract

Excitonic and band-to-band transitions in monolayer WS2 were observed using transient photoconductivity in metal-insulator-silicon structures. Significant improvement in sensitivity was achieved by introducing an Al/WS2 contact scheme. We attribute this improvement to high density of traps in the AlOx interlayer formed at the interface which gives rise to displacement current due to capture of electrons or holes optically generated in WS2. This new method is found to be viable with transferred monolayer films.