Reconfigurable carrier type and photodetection of MoTe 2 of various thicknesses by deep ultraviolet light illumination

Tuning of the Fermi level in transition metal dichalcogenides (TMDCs) leads to devices with excellent electrical and optical properties. In this study, we controlled the Fermi level of MoTe 2 by deep ultraviolet (DUV) light illumination in different gaseous environments. Specifically, we investigated the reconfigurable carrier type of an intrinsic p-MoTe 2 flake that gradually transformed into n-MoTe 2 after illumination with DUV light for 30, 60, 90, 120, 160, 250, 500, 900, and 1200 s in a nitrogen (N 2 ) gas environment. Subsequently, we illuminated this n-MoTe 2 sample with DUV light in oxygen (O 2 ) gas and reversed its carrier polarity toward p-MoTe 2 . However, using this doping scheme to reveal the effect of DUV light on various layers (3–30 nm) of MoTe 2 is challenging. The DUV + N 2 treatment significantly altered the polarity of MoTe 2 of different thicknesses from p-type to n-type under the DUV + N 2 treatment, but the DUV + O 2 treatment did not completely alter the polarity of thicker n-MoTe 2 flakes to p-type. In addition, we investigated the photoresponse of MoTe 2 after DUV light treatment in N 2 and O 2 gas environments. From the time-resolved photoresponsivity at different polarity states of MoTe 2 , we have shown that the response time of the DUV + O 2 treated p-MoTe 2 is faster than that of the pristine and doped n-MoTe 2 films. These carrier polarity modulations and photoresponse paves the way for wider applications of MoTe 2 in optoelectronic devices.