Characterization of Ag adsorption on TiC(001) substrate: an ab initio study
Ma Shang-Yi(马尚义)a)b)† and Wang Shao-Qing(王绍青)a)
a Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; b Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Abstract Ag adsorptions at 0.25--3 monolayer (ML) coverage on a perfect TiC(001) surface and at 0.25 ML coverage on C vacancy are separately investigated by using the pseudopotential-based density functional theory. The preferential adsorption sites and the adsorption-induced modifications of electronic structures of both the substrate and adsorbate are analysed. Through the analyses of adsorption energy, ideal work of separation, interface distance, projected local density of states, and the difference electron density, the characteristic evolution of the adatom-surface bonding as a function of the amount of deposited silver is studied. The nature of the Ag/TiC bonding changes as the coverage increases from 0.25 to 3 MLs. Unlike physisorption in an Ag/MgO system, polar covalent component contributes to the Ag/TiC interfacial adhesion in most cases, however, for the case of 1--3 ML coverage, an additional electrostatic interaction between the absorption layer and the substrate should be taken into account. The value of ideal work of separation, 1.55 J/m$^{2}$, for a 3-ML-thick adlayer accords well with other calculations. The calculations predict that Ag does not wet TiC(001) surface and prefers a three-dimensional growth mode in the absence of kinetic factor. This work reports on a clear site and coverage dependence of the measurable physical parameters, which would benefit the understanding of Ag/TiC(001) interface and the analysis of experimental data.
Received: 23 September 2007
Revised: 28 May 2008
Accepted manuscript online:
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