Doping with Nb enhances the photoresponsivity of WSe2 thin sheets

In this study, we used chemical vapor transport to grow undoped and niobium (Nb)-doped tungsten diselenide (WSe2) thin sheets and then investigated the structural and photoelectronic characteristics of both samples. X-ray photoelectron spectroscopy confirmed the presence of Nb atoms in the Nb-doped WSe2 sample. Hall effect measurements of the transport behavior of the carriers in the undoped and Nb-doped WSe2 indicated that the Nb-doped WSe2 was of p-type and had a higher carrier concentration and lower mobility than the undoped WSe2. The current density–voltage characteristics indicated that doping with Nb led to a decrease in resistance. Photoconductivity measurements revealed that the responsivity of the Nb-doped WSe2 was an order of magnitude greater than that of the undoped WSe2. Thus, doping Nb atoms into WSe2 not only provides effective carriers but also enhances the photoresponsivity significantly. Accordingly, doping WSe2 with Nb atoms would appear to be useful for the fabrication of highly sensitive photodetectors.