Akademik Veri Yönetim Sistemi
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, cilt.24, sa.11, ss.6820-6827, 2022 (SCI-Expanded)
We have carried out an investigation using density functional theory (DFT) of the atomic and electronic structures of SnSe2 layers on the Sn/Si(111)-(root 3 x root 3)R30 degrees surface and hydrogenation of this surface. We have considered a (2 x 2) SnSe2 superstructure oriented along the diagonal direction of the (root 3 x root 3)R30 degrees surface periodicity, for which scanning tunneling microscopy (STM) measurements have recently been reported. In the band structure calculations, while the s-p character surface state originating from each SnSe2 layer is determined, there is an additional half-filled surface state in the fundamental band gap region due to the Sn adatom. At the M point in the Brillouin zone, a charge density wave (CDW) partial gap opening of similar to 0.1 eV occurs between these surface states close to the Fermi level. Here, the CDW gap is caused by two reasons; (i) Fermi surface nesting, due to the inequivalent electron pockets at the M point, and (ii) the out of plane weak electron-phonon coupling regime due to the mean-field (MF) theory (2 Delta/k(B)T(MF) = 3.52). Upon hydrogen adsorption on the Sn/Si(111)-(root 3 x root 3)R30 degrees surface, we have obtained a beta-phase SnSe layer and SeH2 molecule with a bond angle of similar to 90 degrees. The hydrogenated surface pushes the surface state associated with the SnSe2 layer into the Si projected bulk band continuum. After SeH2 desorption, the work function drops from 5.20 eV to 4.39 eV.