First-Principles Studies of Hydrogenated Si(111)--7×\times7

The relaxed geometries and electronic properties of the hydrogenated phases of the Si(111)-7$\times$7 surface are studied using first-principles molecular dynamics. A monohydride phase, with one H per dangling bond adsorbed on the bare surface is found to be energetically favorable. Another phase where 43 hydrogens saturate the dangling bonds created by the removal of the adatoms from the clean surface is found to be nearly equivalent energetically. Experimental STM and differential reflectance characteristics of the hydrogenated surfaces agree well with the calculated features.Comment: REVTEX manuscript with 3 postscript figures, all included in uu file. Also available at http://www.phy.ohiou.edu/~ulloa/ulloa.htm

Photoelectron spectroscopy study of Ag/Si(111)root 3X root 3 and the effect of additional Ag adatoms

High-resolution core-level spectroscopy has been applied to the Ag/Si(111)root3xroot3 surface. The Si 2p line shape is found to depend critically on the presence of additional Ag adatoms on the surface. A significant broadening caused by the surplus of Ag atoms could be eliminated by careful annealing. The resulting Si 2p spectra are significantly sharper than any published data for this or other Si based surface systems. Two major surface components are identified for the root3xroot3 surface, which find a natural explanation in terms of the honeycomb-chained-trimer model. A small but characteristic contribution to the Si 2p spectrum of the Ag/root3xroot3 surface is tentatively assigned to defects

Photoelectron spectroscopy study of Ag/Si(111)√3×√3 and the effect of additional Ag adatoms

High-resolution core-level spectroscopy has been applied to the Ag/Si(111)√3×√3 surface. The Si 2p line shape is found to depend critically on the presence of additional Ag adatoms on the surface. A significant broadening caused by the surplus of Ag atoms could be eliminated by careful annealing. The resulting Si 2p spectra are significantly sharper than any published data for this or other Si based surface systems. Two major surface components are identified for the √3×√3 surface, which find a natural explanation in terms of the honeycomb-chained-trimer model. A small but characteristic contribution to the Si 2p spectrum of the Ag/√3×√3 surface is tentatively assigned to defects

Photoelectron spectroscopy study of Ag/Si(111)√3×√3 and the effect of additional Ag adatoms

High-resolution core-level spectroscopy has been applied to the Ag/Si(111)√3×√3 surface. The Si 2p line shape is found to depend critically on the presence of additional Ag adatoms on the surface. A significant broadening caused by the surplus of Ag atoms could be eliminated by careful annealing. The resulting Si 2p spectra are significantly sharper than any published data for this or other Si based surface systems. Two major surface components are identified for the √3×√3 surface, which find a natural explanation in terms of the honeycomb-chained-trimer model. A small but characteristic contribution to the Si 2p spectrum of the Ag/√3×√3 surface is tentatively assigned to defects

Transition between dynamic regimes in the sputter ablation of Ge(001)

We have studied the dynamic behavior of the Ge(001) surface during sputtering using in situ, real-time synchrotron X-ray diffraction. Two dynamic regimes were found which are characterized by kinetic roughening exponents β of 0.1 and 0.4, respectively. We observed an abrupt transition of the system between these two dynamic regimes both as a function of temperature and ion current. From the boundary between the regimes we derive an activation energy of the relevant diffusion process of 1.1 eV

Surface electronic structure of Ge(001)2 × 1: experiment and theory

Detailed studies of the surface electronic structure of Ge(001)2 × 1 have been performed with angle-resolved photoemission. Five surface structures are identified in the spectra and their initial-energy dispersions E(k∥) are presented along the [010] direction. Employing the local density approximation and Green's functions, the surface band structure along this direction has been calculated self-consistently for an asymmetric dimer model of the 2 × 1-reconstructed surface. Four of the five experimental surface structures are identified with calculated surface states or resonances, i.e. the dangling-bond state and two different back-bond resonances. Excellent agreement is obtained between the experimental and theoretical dispersions for these surface electronic bands