Transport and Photoelectric Properties of 2D Silicene/MX (M = Mo, W; X = S, Se) Heterostructures.

The transport and photoelectric properties of four two-dimensional (2D) silicene/MX (M = Mo, W; X = S, Se) heterostructures have been investigated by employing density functional theory, nonequilibrium Green's function, and Keldysh nonequilibrium Green's function methods. The stabilities of silicene (SiE) are obviously improved after being placed on the MX (M = Mo, W; X = S, Se) substrates. In particular, the conductivities of SiE/MX are enhanced compared with free-standing SiE and MX. Moreover, the conductivities are increased with the group number of X, i.e., in the order of SiE < SiE/MS < SiE/MSe. An evident current oscillation phenomenon is observed in the SiE/WX heterostructures. When a linear light illumination is applied, SiE/MSe shows a stronger photoresponse than SiE/MS. The maximum photoresponse with a value of 9.0 /photon was obtained for SiE/WSe. More importantly, SiE/MS (M = Mo, W) heterostructures are good candidates for application in designing solar cells owing to the well spatial separation of the charge carriers. This work provides some clues for further exploring 2D SiE/MX heterostructures involving tailored photoelectric properties.