Stark Effect Spectroscopy of Mono- and Few-Layer MoS2

We demonstrate electrical control of the A-exciton inter band transition in mono- and few-layer MoS2 crystals embedded into photocapacitor devices via the DC Stark effect. Electric field dependent low-temperature photoluminescence spectroscopy reveals a significant tuneability of the A-exciton transition energy up to similar to 16 meV from which we extract the mean DC exciton polarizability <(beta) over bar (N)> = (0.58 +/- 0.25) x 10(-8) Dm V-1. The exciton polarizability is shown to be layer-independent, indicating a strong localization of both electron and hole wave functions in each individual layer.