Electronic structure tuning of stanene monolayers from DFT calculations: Effects of substitutional elemental doping

Stanene is one of the most important quantum spin hall insulators and can be considered as an efficient material for the fabrication electronic and optoelectronic devices and next-generation integrated circuits. Density functional theory calculations were carried out to investigate the band gap variations in stanene, and the effects of elemental doping were taken into account. For the pristine stanene sheet, the valence and conduction bands of stanene consist of Sn 5p orbitals. The pristine stanene system is a zero band gap material with a Dirac cone located at the K point. The Al-doped, B-doped, N-doped and P-doped systems show metallic characteristics. In the Al-doped and B-doped stanene, the Fermi level is shifted towards the valence band edge, while in the N-doped and P-doped ones, the Fermi level shifts towards the conduction band edge. These doped systems behave as degenerate semiconductors, due to the significant shifts in the Fermi levels. Other doping elements such as Si and Ge were also considered in this study. Both Si and Ge-doped stanene show the properties similar to the pristine stanene, which is a consequence of the similar electronic structure of Si, Ge and Sn atoms. In the N-doped stanene, the Dirac cone vanishes, whereas in the other doping patterns, the Dirac cone exists around the Fermi level. The electronic band structure of the Si and Ge-doped systems is principally the same as that of pristine one. Our results thus suggest a theoretical basis for the potential application of such doped systems in electronic and optoelectronic devices.