Initial stages of Pt growth on Ge(001) studied by scanning tunneling microscopy and density functional theory

We have studied the initial stages of submonolayer Pt growth on the Ge(001). We have observed several stable and meta-stable adsorption configurations of Pt atoms at various temperatures. Calculations indicate relatively high binding energies of Pt atoms onto the Ge lattice, at different adsorption sites. Our results show that through-the-substrate bonding (concerted bonding) of two Pt atoms is more favored on Ge(001) surface then a direct Pt-Pt bond. Both our experiments and calculations indicate the breaking of Ge-Ge bonds on the surface in the vicinity of Pt adsorbates. We have also observed the spontaneous generation of 2 + 1 dimer vacancy defects at room temperature that cause the ejection of Ge atoms onto the surface. Finally we have studied the diffusion of Pt atoms into the bulk as a result of annealing and found out that they get trapped at subsurface sites