Electrical control of optical properties of monolayer MoS2

We investigate electrical gating of photoluminescence and optical absorption in monolayer molybdenum disulfide (MoS2) configured in field effect transistor geometry. We observe a hundredfold increase in photoluminescence intensity and an increase in absorption at ∼660 nm in these devices when an external gate voltage is decreased from +50 to −50 V, while the photoluminescence wavelength remains nearly constant. In contrast, in bilayer MoS2 devices we observe almost no changes in photoluminescence with gate voltage. We propose that the differing responses of the monolayer and bilayer devices are related to the interaction of the excitons in MoS2 with charge carriers.