Piezoelectricity enhancement and bandstructure modification of atomic defect-mediated MoS monolayer.

Piezoelectricity appears in the inversion asymmetric crystal that converts mechanical deformation to electricity. Two-dimensional transition metal dichalcolgenide (TMDC) monolayers exhibit the piezoelectric effect due to inversion asymmetry. The intrinsic piezoelectric coefficient (e) of MoS is ∼298 pC m. For the single atomic shift of Mo of 20% along the armchair direction, the piezoelectric coefficient (e) of MoS with 5 × 5 unit cells was enhanced up to 18%, and significantly modified the band structure. The single atomic shift in the MoS monolayer also induced new energy levels inside the forbidden bandgap. The defect-induced energy levels for a Mo atom shift along the armchair direction are relatively deeper than that for a S atom shift along the same direction. This indicates that the piezoelectricity and band structure of MoS can be engineered by a single atomic shift in the monolayer with multi unit cells for piezo- and opto-electric applications.