Adsorption process and 2=1l1=1 phase transition of Sb–dimer on Si 001/and Ge 001/surfaces

We investigate the initial process of adsorption of Sb–dimer on Si 001.–1=2 and Ge 001.–1=2 surfaces, considering a number of possible geometric configurations. Furthermore, we determinate the energy barrier relatively to the 2=1l1=1 phase transition of the Si 001.rSb and Ge 001.rSb surfaces. The calculations were performed within the local density approximation LDA., using a norm conserving and ab initio fully separable pseudopotentials. Our results indicate that the adsorption of Sb–dimer, perpendicular and over the substrate Si Ge.–dimers row, is the energetically more favourable configuration. In this adsorption process the substrate Si Ge.–dimer bond is conserved, reducing the number of the surface dangling bonds. The dissociation process of the adsorbed Sb–dimer, corresponding to the 2=1l1=1 phase transition, presents an energy barrier equal to 0.39 eVrdimer and 0.53 eVrdimer, on Si and Ge surfaces, respectively. q1999 Elsevier Science B.V. All rights reserved