The (112) surface of group-IV semiconductors and properties of PtSi : a first principle study
First principle calculations on the (112) surface of the group-IV elements diamond, silicon, germanium and α-tin were carried out within the framework of Density Functional Theory (DFT). We report chemical trends in surface energies, reconstructions and work functions. In addition we investigate two models for the 7x1 indium induced reconstruction of the silicon (112) surface by means of adsorption energies and STM simulations. We find a substitutional model to be favorable compared to on-terrace adsorption in good agreement with LEED and STM experiments. A drop of 0.46 eV in the work function due to the adsorption is found. Furthermore, we investigate the electrical and optical properties of the two room temperature stable silicide phases PtSi and Pt2Si. Experimental data on optical constants is provided and found to be in good qualitative agreement with the theory. Among various orientations the (121) surface of PtSi has the lowest calculated surface energy. This orientation also produces the distinctively highest peak in an X-ray spectrum of a 300 Å film of PtSi. We demonstrate theoretically that PtSi surfaces can perform reconstructions with similar energy gains as known for semiconductor surfaces.