Research Of The Ge(111)-Ag And Ag(111)-Ge Adsorption Structures

The adsorption properties of metal atoms on semiconductor and the structural changes of semiconductor atoms adsorb on metal surface are all important subjects in semiconductor device physics and modern electronic industry. Research on the structural properties of metal-semiconductor surface and interface is important in getting deep understanding for surface mechanism and adsorption process mechanism, and developing new materials. In this paper, the geometrical structures and electronic properties for the Ge(111) surface, Ge(111)-Ag, Ag(111) surface, and Ag(111)-Ge systems have been studied using the CASTEP simulation software, which is based on the plane wave basis set and ultrasoft pseudopotential in the first-principle calculations. The properties of semiconducture-metal surface and interface are studied systematically, by systematically calculating the surface energy, adsorption energy, work function, Mulliken population analysis, density of states, etc. Firstly, the structural parameters of Ge(111) and Ag(111) surfaces and their surface electronic properties calculated are in agreement with experimental results. It confirms that the simulating methods and models are correct. Secondly, for the adsorption systems, the adsorption atoms prefer to be adsorbed at the adsorption sites with more coordinate atoms. Thirdly, a small amount of charges transter between Ag atoms and Ge atoms in the adsorption process, because the electro-negativities of Ag and Ge atoms are very close. very close of Ag and Ge atoms. And the interactions between adsortion atoms and the surface atoms are weak. Ag and Ge mixed layer doesn't exist. For the Ge(111)-Ag systems, the chemical activity of Ge(111) surface is enhanced by the adsorption of Ag atoms. While the energy bands spectra of the 0.5ML covered surface is of metallic nature, and 1ML covered suface leads to a semiconducting surface. For the Ag(111)-Ge systems, adsorbed Ge atoms induce formation of the Ag(111) surface folds, and lead the work function of Ag(111) surface to decrease slightly because of forming dipole moment between Ge atoms and surface Ag atoms. With the coverage increase and Ge atoms moving away from Ag (111) surface, Ge-Ag interactions weakened, and Ge-Ge interactions increasing.