First Principle Investigations of Structural, Electronic and Thermal Properties of Pristine, Metal and Non-Metal Doped Silicene for Thermoelectric Applications

Abstract

Silicene, a two-dimensional hexagonal silicon layer, exhibits exceptional electronic and thermoelectric properties. However, its application  in semiconductors is hindered by its zeroband gap, which could be overcome by modifying its electronic properties through  doping. In this paper, Density Functional Theory (DFT) calculations were performed to investigate the band gap opening in silicene by  studying the effect of magnesium and sulphur doping on its electronic, structural and thermal properties. Pristine silicene has a lattice  constant of 3.86 Å and a zero-band gap. Upon doping with 12.5% S and Mg atoms, the lattice constant modifies to 3.45 Å and 3.93 Å,  respectively, resulting in a direct band gap opening. For 25% Mg and S doping, the result shows that Mg and S effectively alter the band  structure and the band gap of silicene monolayer at various configurations. The maximum band gap was 0.98 eV and 1.22 eV for Mg and  S doping into the meta position to the reference point R, respectively. The power factor significantly increases with doping, reaching 1.20  x 1011 WK-2m-1 and 1.40 x 1011 WK2m-1 for 12.5% Mg and S doping compared to 7.4 x 1010 WK-2m-1 for pristine silicene. This substantial enhancement indicates improved thermoelectric performance, making silicene a promising candidate for thermoelectric  applications. Results demonstrate that tuning the band gap through doping can simultaneously enhance the power factor, highlighting  the potential of Mg/S-doped silicene for efficient energy harvesting and conversion.