Laser-Induced Engineering of Surface Structures and Properties on Oxygen-Adsorbed TiC(111) Surface: First-Principles Calculations

摘要

In this chapter, we used the density functional theory (DFT) to systematically investigate the electron structure and elastic moduli of oxygen-adsorbed 0/Ti_xC_y(111) surface affecting its potential reconstructions with laser. For the first time we studied within the density functional theory framework the local atomic and electron structures of potential O/Ti_xC_y(111) surface configurations as well as their thermodynamic and elastic properties. A considerable rearrangement has been established in the local atomic structure of O/TiC(111) surface depending upon the degree of its coverage with atomic oxygen in FCC stacking position. We have demonstrated that the distance between adsorbate and TiC(lll) surface decreased with the increase of its coverage with oxygen. Additionally, the effect of oxygen adsorbed on the Ti_xC_y(111) surface on the electronic properties in its different reconstructions has been also studied. The results showed that a correlation between the energy level of flat bands in the -5.1 eV and -5.7 eV energy regions was responsible for the doublet of singular peaks corresponding to partial densities of oxygen 2p electrons, and the bond energy and adsorption energy of oxygen atom in non-stoichiometric O/TiC_y(111) systems. Effective charges of titanium and carbon atoms surrounding the oxygen adatom in various reconstructions have been identified. We have established charge transfer from titanium atom to oxygen and carbon atom,s determined by the reconstruction of local atomic and electron structures and correlating with their electronegativity values and chemisorption processes. Calculated values of elastic moduli for the upper part of ultrathin O/TiC (111) and O/Ti_xC_y(111) layers correlate well with experimental findings and other theoretical results. Potential mechanisms for laser nanostructuring of titanium carbide surface have been suggested.