First-principles Study On The Electronic Properties Of Physical And Chemical Adsorption Of Silicene

First-principles calculation method is used based on the density functional theory.The VASP software is mainly used for the adsorption calculation of the prestine silicene.The band structure and electronic structure were calculated with atoms adsorped on silicene surface such as non-metallic B and metals Cr,Mo and Pt.Carry out calculations to explore the effect of chemisorption on the electronic structure of silicene,in order to open the band gap of silicene.Stack silicene and h-BN vertically to form a heterojunction,and then explore physical adsorption using interlayer forces to change the electronic structure of silicene,in order to adjust the band structure.Studies have shown that the most stable adsorption site of non-metallic atom B and metal atom Mo on the surface of silicene are valley sites,and the adsorption energies are-4.08 e V and-7.57 e V,respectively.The most stable adsorption sites of metal atoms Cr and Pt atoms are hollow sites.The adsorption energy are-7.71 e V and-6.28 e V,respectively.During the process of atom adsorption in silicene,charge transfer occurs between Si atoms with adsorbed atoms,which is chemical adsorption.Part of the adsorption sites generate magnetic moments due to the spin-polarized structure.The bridge site adsorption B atom structure generates 0.67μB magnetic moments,the hill and hollow adsorption Mo atom structure generates 5.31μB and 3.06μB magnetic moments.The hill site,hollow site and valley site adsorption of Cr atomic generates5.86μB,4.39μB and 3.99μB magnetic moments,respectively.The prestine silicene is a zero-band-gap semi-metallic structure,and the band gap of the adsorbed atoms in different adsorption site has different degrees of opening.The silicene with Cr atoms and Mo atoms are adsorbed at the hill site both open 0.21 e V band gap,resulting in a flat band structure below the Fermi level.The hill-adsorption Pt atom silicene band gap opens 0.3e V,producing a flat band structure above the Fermi level.The silicene with B atom adsorption at the bridge site opened 0.15 e V direct band gap.The silicene with Cr atom adsorption at the valley site opened a 0.2e V direct band gap,and the silicene with Mo atom adsorption at the hollow site and valley site opened the direct band gap of0.04 e V and 0.26 e V,respectively.The silicene with Pt atom adsorption at the hollow and valley sites opened the direct band gap of 0.04 e V and 0.08 e V,respectively.The Dirac cone remains intact while the band gap is opened.Although the band gaps of other adsorption sites are opened to different degrees,the bottom of the conduction bandpasses through the Fermi level and is still a semi-metallic structure.The heterojunction is formed by silicene with h-BN stacking.Due to the physical adsorption between silicene layer with h-BN layer,the band gap of silicene is opened.Through differential charge density calculation,it is found that an electric field is built between the silicene with the h-BN.The holes are mainly concentrated on the silicene side,while the electrons are concentrated on the h-BN side.Between the silicene and the h-BN,a long wave of polarization is generated.Due to the difference between the band gap of silicene and h-BN,the phenomenon of band alignment occured in the heterojunction.Sh-1 and Sh-2 band gaps open 0.72 e V,which is a direct band gap semiconductor,and Sh-3 opens 0.06 e V direct band gap,and produced 6.68μB magnetic moment.