devices

Single layer semiconducting transition metal dichalcogenides (TMD) are direct band gap
semiconductors that exhibit a variety of novel phenomena, ranging from valley hall effect to
highly correlated electron physic. However, the transport studies of many of these phenomena
have been hindered by low mobility, defective TMD materials. While the defect density of
commercially grown TMD can be higher than 0.1%, in this work we use flux grown TMD
samples with defect density significantly reduced to 0.01%. We report unprecedently high hole
mobility values of up to 30,000 cm²/V.s in single layer (1L) WSe₂ encapsulated in between hBN
single crystals. Unlike that of conventional semiconductors, mobility of flux grown WSe₂
devices increases with reduced carrier density, indicating that mobility is not dominated by
charged impurities. We find the quantum scattering time, tau_q, to be ~400 ps, similar to tau_q
in graphene devices. Moreover, by preforming photoluminescence spectroscopy, we find
extremely sharp exciton linewidth (>1meV) and other optical features such as dark excitons and
biexcitons.