Structure analysis of the TiC(001) surface with transition metal impurities (Zr, Nb, Mo)

The surface structures of TiC(001) crystals with dilute transition metal im purities heated up to around 2000 K (0.6 wt.% of Zr, Nb and Mo) have been i nvestigated by an Li+ impact collision ion scattering spectroscopy combined with a three dimensional three-atom computer simulation. The TiC(001) surf ace shows the 1 x 1 structure before and after segregation of the impuritie s and the impurity atom of these metals substitutes for the Ti atom at the topmost surface layer. The group VIa impurity, such as Mo, is segregated at the TiC(001) surface with carbon vacancies in their nearest neighbors, but the group IVa and Va metal (Zr and Nb) impurities are segregated without t he carbon vacancies. The segregated impurity atoms are located at levels sh ifted somewhat from the TiC(001) surface. (C) 2000 Elsevier Science B.V. Al l rights reserved.