M.C. Håkansson

The adsorption of I2 on Si(111)-7×7 studied by soft X-ray photoemission

The adsorption Of I2 on Si(111)-7 x 7 at room temperature is studied with soft X-ray photoelectron spectroscopy. I2 adsorbs dissociatively, forming a mixture of SiI, SiI2 and SiI3 moieties, of whic ...

The electronic structure of In- and As-terminated InAs(001) surfaces

Abstract The InAs(001) 2 × 4 and 4 × 2 surfaces have been investigated by angle-resolved photoemission. The X 3 and X 5 points were found to be located 6.0 and 2.7 eV below the valence band maximum, respectively, and the dispersion of bulk bands along the Г-X direction in the bulk Brillouin zone were well described by a theoretical calculation. From angle-resolved valence band spectra measured along the high symmetry directions [110] and [110], three surface induced states were identified on both the InAs(001)4 × 2 and the InAs(001)2 × 4 surface.

ROLE OF SURFACE STOICHIOMETRY IN THE CL2/GAAS(001) REACTION

The room‐temperature reaction of Cl2 with GaAs(001)‐4×6, ‐c(2×8), and ‐c(4×4) surfaces is studied with synchrotron soft x‐ray photoelectron spectroscopy. The chemical composition of the reacted surfaces is found to depend on the stoichiometry of the starting surface. In all cases, the reaction occurs stepwise, with Ga and As monochlorides formed prior to the dichlorides. The Ga‐rich surface is initially more reactive than either of the As‐rich surfaces and it forms more GaCl than the As‐rich surfaces, which instead form more AsCl. The sticking coefficient for chlorine on GaAs(001) decays exponentially with coverage. A contribution from Cl atoms comprising the surface dichlorides is identified in the Cl 2p core‐level spectra.

Sputtered and annealed InAs(111) : an unreconstructed surface

The electronic structure of the InAs(111)1 × 1 surface has been investigated by angle resolved photoelectron spectroscopy along the symmetry lines ΓK, ΓM, and ΓM′ of the surface Brillouin zone. The bulk valence band structure was calculated using a combination of the linear augmented plane-wave method and the relativistic augmented plane-wave method. We have projected the theoretical bulk band structure onto the surface Brillouin zone to separate surface states from surface resonances. Two surface related structures, S1 and S2, have been observed and their Ei(k‖) dispersions are established. Both S1 and S2 show the symmetry of the 1 × 1 surface Brillouin zone, which is consistent with the observed 1 × 1 LEED pattern. We identify S1 as the As-derived dangling bond state, and S2 is associated with the backbonds connecting the As atoms in the surface layer with the underlying In layer.

Surface atomic structure of InAs(1̄1̄1̄)2 × 2 and InSb(1̄1̄1̄)2 × 2 studied by core level spectroscopy

Abstract Surface sensitive high resolution core level spectroscopy has been applied to the molecular beam epitaxy grown InAs ( 1 1 1 )2 × 2 and InSb ( 1 1 1 )2 × 2 surfaces. For both systems the In 4d core level consists of one dominating component while the Group V core levels are deconvoluted into four components. This analysis is consistent with a surface model where the topmost layer consists entirely of arsenic or antimony. In this model, Group V atoms form trimers bound to Group V atoms in the first double layer, leaving a single Group V rest atom per unit cell.

Angle-resolved photoemission spectroscopy of the 1 × 1 ordered overlayers on iodine-saturated GaAs(001) and InAs(001)

Angle-resolved valence band photoelectron spectra are collected from 1 X 1 ordered overlayers on 12-saturated GaAs(001)-4 X 1, -c(2 X 8), and InAs(001)-c(8 X 2). A high-intensity dispersive surface state, located approximately 4.4 eV below the valence band maximum, is observed in each case. The state passes through an open lens in the projected bulk density of states and disperses symmetrically around the surface Brillouin zone edge. For all surfaces studied, the state is stronger when excited with the electric field polarized in the [110], as compared to the [110], azimuth. Since the state is independent of the termination of the initial surface, and since iodine bonds primarily to the outermost element, the state must result from delocalization of the electron states in the overlayer, and is not related to bonding with the substrate.

Photoemission study of low coverage potassium adsorption on the Si(111)1 × 1:As surface

Deposition of small amounts of potassium on the As-terminated Si(111) surface results in the population of the empty surface resonance state around the M-point in the surface Brillouin zone and a band bending shift of 0.65 eV, which leads to a Fermi level pinning above the conducting band minimum. By using angle resolved photoemission we have directly measured the surface band gap between the empty resonance state and the lone-pair state to be 1.8 eV. This result is in excellent agreement with recent quasi-particle bandstructure calculations.

Surface electronic structure of InSb(100) 4 × 1 studied by angle-resolved photoelectron spectroscopy

The surface electronic structure of the In-rich InSb(100)4 X 1 surface has been studied by angle-resolved photoelectron spectroscopy. To determine the origin of different contributions in spectra, direct bulk interband transitions were first identified using a semi-empirical band structure calculation and assuming direct transitions into free electron-like final bands. Three surface-induced features were identified and their dispersions have been mapped along symmetry directions of the surface Brillouin zone.

Dimer formation and electronic structure on the Ge(100)(2 × 1): Sb surface

Deposition of antimony on Ge(100)2 X 1 results in a well-ordered, highly passivated surface. From a comparison between core-level data and angle-resolved photoemission data, we conclude that the ob ...

Identification of surface states at the CdTe(110) surface by means of Cs adsorption

Angle-resolved photoelectron spectra are reported along the GAMMA-YBAR and YMBAR directions in the surface Brillouin zone from the CdTe(110) surface, before and after Cs adsorption. By studying the Cs induced spectral modifications we are able to identify surface states of the clean surface. On the whole, the results support our previous assignments, which were based on other identification criteria. We find, however, that the contamination test provides new important information, particularly in cases where surface derived emission is close to-bulk emission.