  Piezoelectricity appears in the inversion asymmetric crystal that converts
mechanical deformational force to electricity. Two-dimensional transition metal
dichalcolgenide (TMDC) monolayers exhibit the piezoelectric effect due to the
inversion asymmetry. The intrinsic piezoelectric coefficient (e11) of MoS2 is
~298 pC/m. For the single atomic shift of Mo of 20% along the armchair
direction, the piezoelectric coefficient (e11) of MoS2 with 5x5 unit cells was
enhanced up to 18%, and significantly modified the band structure. The single
atomic shift in the MoS2 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 the energy levels for a S
atom shift along the same direction. It indicates that the piezoelectricity and
band structure of MoS2 can be engineered by a single atomic shift in the
monolayer with multi unit cells for mechano-electrical applications.
