Transistor properties of exfoliated single crystals of 2H-Mo(S e1-x T ex)2 (0≤x≤1)

Field-effect transistors (FETs) were fabricated using exfoliated single crystals of Mo(Se1-xTex)2 with an x range of 0 to 1, and the transistor properties fully investigated at 295 K in four-terminal measurement mode. The chemical composition and crystal structure of exfoliated single crystals were identified by energy-dispersive x-ray spectroscopy (EDX), single-crystal x-ray diffraction, and Raman scattering, suggesting the 2H- structure in all Mo(Se1-xTex)2. The lattice constants of a and c increase monotonically with increasing x, indicating the substitution of Se by Te. When x<0.4 in a FET with a thin single crystal of Mo(Se1-xTex)2, n-channel FET properties were observed, changing to p-channel or ambipolar operation for x>0.4. In contrast, the polarity of a thick single-crystal Mo(Se1-xTex)2 FET did not change despite an increase in x. The change of polarity in a thin single-crystal FET was well explained by the variation of electronic structure. The absence of such change in the thick single-crystal FET can be reasonably interpreted based on the large bulk conduction due to naturally accumulated electrons. The μ value in the thin single-crystal FET showed a parabolic variation, with a minimum μ at around x=0.4, which probably originates from the disorder of the single crystal caused by the partial replacement of Se by Te, i.e., a disorder that may be due to ionic size difference of Se and Te.