First-principles study of the optical and thermoelectric properties of 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.

Thermoelectric properties of armchair graphene nanoribbons with array characteristics

The thermoelectric properties of armchair graphene nanoribbons (AGNRs) with array characteristics are investigated theoretically using the tight-binding model and Green's function technique. The AGNR structures with array characteristics are created by embedding a narrow boron nitride nanoribbon (BNNR) into a wider AGNR, resulting in two narrow AGNRs. This system is denoted as w-AGNR/n-BNNR, where 'w' and 'n' represent the widths of the wider AGNR and narrow BNNR, respectively. We elucidate the coupling effect between two narrow symmetrical AGNRs on the electronic structure of w-AGNR/i-BNNR. A notable discovery is that the power factor of the 15-AGNR/5-BNNR with the minimum width surpasses the quantum limitation of power factor for 1D ideal systems. The energy level degeneracy observed in the first subbands of w-AGNR/n-BNNR structures proves to be highly advantageous in enhancing the electrical power outputs of graphene nanoribbon devices.

Tunable band gap and enhanced thermoelectric performance of tetragonal Germanene under bias voltage and chemical doping

This paper employs the tight-binding model to investigate the thermal properties of tetragonal Germanene (T-Ge) affected by external fields and doping. T-Ge is a two-dimensional material with unique electronic properties, including zero band gap and two Dirac points. The electronic properties of T-Ge can be influenced by bias voltage, which can open its band gap and convert it to a semiconductor due to its buckling structure. The tunable band gap of biased T-Ge, makes it a a promising option for electronic and optoelectronic devices. The band structure of T-Ge is split by the magnetic field, leading to an increases its band edges due to the Zeeman Effect. The findings demonstrate that the thermoelectric properties of T-Ge are highly sensitive to external parameters and modifications of the band structure. The thermal and electrical conductivity of T-Ge increase with increasing temperature due to the rise in thermal energy of charge carriers. The thermoelectric properties of T-Ge decrease with bias voltage due to band gap opening, increase with the magnetic field due to a modifications of the band structure, and increase with chemical potential due to increasing density of charge carriers. By manipulating the band structure of T-Ge through bias voltage and chemical doping, the electrical conductivity can be optimized to achieve higher figure of merit (ZT) and improved thermoelectric performance. The results demonstrate the potential of T-Ge for use in electronic and magnetic devices, opening up new possibilities for further research and development in this field.