Biaxial strain modulated the electronic structure of hydrogenated 2D tetragonal silicene

Electric field modulated electronic, thermoelectric and transport properties of 2D tetragonal silicene and its nanoribbons

Using both first principles and analytical approaches, we investigate the role of a transverse electric field in tuning the electrical, thermoelectric, optical and transport properties of a buckled tetragonal silicene (TS) structure. The transverse electric field transforms the linear spectrum to parabolic at the Fermi level and opens a band gap. The gap is similar at the two Dirac points present in the irreducible Brillouin zone of the TS structure and increases in proportion to the applied field strength. However, a sufficiently strong electric field converts the system into a metallic one. A comparable band opening is also seen in the TS nanoribbons. Electric field-induced semiconducting nature improves its thermoelectric properties. Estimated Debye temperature reveals its superiority over graphene in terms of thermoelectric performance. The optical response of the structures is very asymmetric. Large values of imaginary and real components of the dielectric function are seen. The absorption frequency lies in the UV region. Plasma frequencies are identified and are red-shifted with the applied field. The current-voltage characteristics of the symmetric type nanoribbons show oscillation in current whereas the voltage-rectifying capability of anti-symmetric type nanoribbons under a transverse electric field is interesting.

First-principles study of the optical and thermoelectric properties of tetragonal-silicene

We report the optical and thermoelectric properties of the two-dimensional Dirac material T-silicene (TS) sheet and nanoribbons (NRs) by first-principles calculations. Both the optical and thermoelectric properties of TS can be modified by tailoring the sheet into nanoribbons of different widths and edge geometries. The optical response of the structures is highly anisotropic. A π interband transition occurs in the visible range of incident light with parallel polarization. The optical response for asymmetric arm-chair TS nanoribbons (ATSNRs) is larger than for symmetric ATSNRs. The absorptions of asymmetric ATSNR are redshifted due to a decrease in the bandgap with the width of the NRs. Plasma frequencies of the sheet and the NRs are identified from the imaginary part of the dielectric function and electron energy loss spectra curves. Thermoelectric properties like electrical conductivity, Seebeck coefficient, power factor, and electronic figure of merit are also studied. Compared with graphene, the TS sheet possesses a higher electrical conductivity and a better figure of merit. Among the NRs, asymmetric ATSNRs exhibit a better thermoelectric performance. All these intriguing features of TS may shed light on fabricating smart opto-electronic and thermoelectric devices.