Spectral density of surface states: Clean W(001) surface

The transfer matrix approach is applied to calculate the spectral density of electronic states for the W(001) surface. We use a tight-binding hamiltonian with a nine function basis: 6s, 6p and 5d. Results for $\text{k}$ points along the Σ and ? symmetry lines are presented for occupied states. Both surface and bulk features of the spectral density are in good agreement with angularly resolved photoemission spectra.     

Band edge singularities and the surface density of states in Nb (110)

Photoemission measurements of the Nb(110) surface show surface sensitive structure near the Fermi energy which can be attributed to bulk band structure effects persisting right out to the surface layer, in agreement with recent layer density of states calculations for Mo(110).     

Spin-resolved photoemission of surface states of W(110)-(1 x 1)H

The surface electronic states of W(110)-(1 x 1)H have been measured using spin- and angle-resolved photoemission. We directly demonstrate that the surface bands are both split and spin-polarized by the spin-orbit interaction in association with the loss of inversion symmetry near a surface. We observe 100% spin polarization of the surface states, with the spins aligned in the plane of the surface and oriented in a circular fashion relative to the Smacr; symmetry point. In contrast, no measurable polarization of nearby bulk states is observed.     

Diffusion of tungsten clusters on tungsten (110) surface

Using molecular dynamics simulation and modified analytic embedded-atom method, we have investigated the self-diffusion of clusters on a tungsten (110) surface. As compared to the linear-chain configuration, the close-packed islands for tungsten clusters containing more than nine adatoms have been predicted to be more stable with the relatively lower binding energies. The migration energies show an interesting and oscillating behavior with increasing cluster size. The tetramer, hexamer and octamer have obviously higher migration energies than the others. The different atomic configurations and diffusion mechanisms have been determined during the diffusion processes. It is clear that the dimer-shearing mechanism occurs inside the hexamer, while it occurs at the periphery of heptamer. The successive hopping mechanism of individual atom is of critical importance in the migration of the clusters containing five or fewer adatoms. In addition, the diffusion of a cluster with nine adatoms is achieved through the changes of the cluster shape.     

Metastable surface structureof the W(110) face

The observation of a new metastable phase on the (110) tungsten surface contaminated with carbon is reported with an explanation based on a model of surface deformation in the (110) plane. The transition from the stable C1 structure to the metastable C2 structure is reversible and this cycle is reproducilbe.     

Surface states,local bonding,and surface reconstruction: Na on Cu(110)

Occupied and unoccupied surface states on Na/Cu(110) have been investigated by photoemission and inverse photoemission. By measuring surface state positions at the same adsorbate coverage on the reconstructed and the unreconstructed surface it is demonstrated that the surface states contribute to the total energy balance of the Na induced missing row reconstruction. During the onset of the reconstruction an up-shift of the surface states depopulates an initially occupied CuCu bonding surface state and consequently destabilizes the topmost Cu atoms. The surface state wavefunctions are qualitatively analyzed in a thight-binding LCAO picture.     

Ultra thin Al film on the W(110) surface

We have investigated the surface structure of the Al/W(110) surface using low energy electron diffraction (LEED) and low energy ion scattering spectroscopy (ISS). We observe a p(2 × 1) double domain LEED image for the 0.5 ML Al/W(110) surface at annealing temperature 850 °C. We found that 0.5 ML Al atoms cover on the W(110) surface uniformly but do not form 3 or 2-dimensional islands. We also measured the Al adsorption site at the Al/W(110)-p(2 × 1) surface using ISS. We found that Al atoms adsorbed at the center of the bridge site. The height of the adsorbed Al atoms is determined to be 2.18 ± 0.15 Å above the W surface layer.     

Comparison between Rydberg surface resonances on W(001) and W(110)

Comparison is made between high-resolution LEED measurements of electronic surface resonances in the (00) beam from W(001) and W(110). The study of W(110) extended to several polar angles of incidence provides new information that helps to explain the data obtained on W(001) at a fixed angle.     

Rhenium on W(110): Structure and mobility of higher clusters

Rhenium tetramers, pentamers, and larger clusters have been formed on W(110) and examined in the field ion microscope. Tetramers and pentamers exist in different configurations, but an open, ringlike structure predominates at high temperatures. In this configuration none of the component adatoms are in nearest neighbor sites, and the atoms can be individually resolved. The mobility of these open clusters has been explored, and found to be considerably higher than that of tri mers, or of larger aggregates.     

Optical detection of surface states in GaAs(110) and GaP(110)

We present results on the optical detection of surface states in GaAs(110)and GaP(110)by the method of the fractional change of external reflectivity. Optical transitions are observed at ～3.1 eV m GaAs(110) and ～3.4 eV in GaP. A comparison with existing theories suggests a rotational relaxation model for the surface, with partial relaxation for GaAs(110) and full relaxation for GaP(110).     

Long jump rates in surface diffusion: W on W(110)

We have reexamined the diffusion of W adatoms on W(110) using the field ion microscope. The diffusivity is in good agreement with previous results and reveals no unusual features, but from observations of the distribution of displacements, corrected for diffusion during temperature transients, we have for the first time been able to measure the temperature dependence of rates for nearest-neighbor and double jumps, as well as for vertical and horizontal transitions. Activation energies and frequency factors for all the long jumps are significantly larger than for single jumps, and a simple model is proposed to account for our observations.     

Density of states of the clean Mo (110) surface

The electronic structure of the (110) surface of Mo is calculated using transfer matrix method. The Hamiltonian is of tight-binding type with a basis of nine orbitals per atom. Spectral densities of states for special points of the 2-D Brillouin zone are presented on the surface and in the three consecutive layers. The band structure in the σ direction and the local density of states are also calculated. The results are compared with the few experimental data available in the literature.     

Electronic states induced by surface defects on GaSb(110)

Electronic state calculations for point defects on the GaSb(110) surface are presented using a cluster, in order to indicate theoretically the usefulness of the defect model as a mechanism of the Fermi level pinning in Schottky barriers. The results demonstrate that the presence of atomic Ga at surface Sb vacancy sites in addition to surface Ga vacancies gives electronic states localized near the top of the valence band which can be responsible for the pinning observed experimentally.     

Surface states and metal overlayers on the (110) surface of GaAs

We have found new surface states related to Al overlayers on the (110) surface of GaAs. These states play a prominent role in the determination of the electronic structure for metal-semiconductor interfaces. The results are consistent with conjectures of Rowe, Christman and Margaritondo based upon recent experimental results for metal overlayers on semiconductor surfaces.