Adsorption Of Alkali Metal Atoms On Two-dimensional GeSi Alloy Sheet

Since graphene has been discovered 13 years ago, owing to its extremely high carrier mobility, its has attracted enormous attention around the world. On account of silicon and germanium are the first generation of semiconductor material, also are the basis of modern microelectronics industry and information industry. Thus in recent years,the silicene as well as germanene as graphene counterpart in silicon and germanium has become the focus of research. It is found that there are better properties of silicene as well as germanene, such as the quantum spin Hall effect. In this paper, by orderly substituting Si(Ge) atoms by Ge(Si) atoms in silicene(germanene), the two-dimensional ordered GeSi alloy sheet (GeSiAS) is demonstrated. The specific research contents are listed below:The structural and electronic properties of both bare and alkali metal(AM) atoms adsorbed two-dimensional GeSi alloy sheet (GeSiAS) are investigated by means of first-principles calculations. The band gaps of bare GeSiAS are shown slightly opened at Dirac point with the energy dispersion remain linear due to the spin-orbit coupling effect at all concentrations of Ge atoms. For metal adsorption, AM atoms (including Li, Na and K) prefer to occupy the hexagonal hollow site of GeSiAS and the primary chemical bond between AM adatom and GeSiAS is ionic.The adsorption energy has an increase tendency with the increase of the Ge concentration in supercell. Besides, single-side adsorption of AM atoms introduces band gap at Dirac point, which can be tuned by the Ge concentration and the species of AM atoms. The strong relation between the band gaps and the distribution of Si and Ge atoms inside GeSiAS are also demonstrated. The opened band gaps of AM covered GeSiAS range from 14.8 to 269.1 meV along with the effective masses of electrons ranging from 0.013 to 0.109 me, indicating the high tunability of band gap as well as high mobility of carriers. These results provide a development in two-dimensional alloys and show potential applications in novel micro/nano-electronic devices.