S. Kono

Surface electronic structure of a single-domain Si(111)4×1-In surface : a synchrotron radiation photoemission study

The electronic structure of a Si(111)4 × 1-In surface has been studied by angle-resolved photoelectron spectroscopy (ARPES). Using a 1.1° off-axis Si(111) wafer as substrate, a single-domain Si(111)4 × 1-In surface has been prepared in order to determine the dispersion of surface state (SS) without the obscurity arising from multi-oriented 4 × 1 domains. Three SSs that cross the Fermi level have been found. Thus, the Si(111)4 × 1-In surface is concluded to be metallic. The dispersions of the metallic SS appeared to be almost one-dimensional, suggesting one-dimensional metallic bonds among In atoms. Completely occupied SSs have been also found. The characteristics of SSs are discussed in relation to the existing structural models for the Si(111)4 × 1-In surface.

Study of Ag/Si(111) submonolayer interface: I. Electronic structure by angle-resolved UPS

Abstract Angle-resolved ultraviolet photoelectron spectra have been measured for well defined Ag/Si(111) submonolayer interfaces of (1) Si(111)( 3 × 3 )R30°-Ag , (2) “Si(111)(6 × 1)-Ag”, and (3) Ag/Si(111) as deposited at room temperature. Non-dispersive and very narrow (FWHM ∼ 0.4–0.5 eV) Ag 4d derived peaks are found at 5.6 and 6.5 eV below the Fermi level for surface (1) and at 5.3 and 6.0 eV for surface (2). Dispersions of sp “binding” states in the energy range between E F and Ag 4d states have been precisely determined for surface (1). Electronic structures similar to those of the Ag(111) surface, including the surface state near E F , have been observed for surface (3).

Angle-resolved ultraviolet photoemission study of Si(111) 7 × 7 and 1 × 1 surfaces

Abstract Angle-resolved ultraviolet photoelectron spectra of Si(111) 7 × 7 and 1 × 1 surfaces have been measured as a function of temperature from ambient temperature to ≈ 1120°C. Both the Si(111) 7 × 7 and 1 × 1 surfaces show obvious surface metallic edge at all the temperatures. A middle peak among three surface-state peaks observed for ambient-temperature 7 × 7 surface has been found to disappear for high-temperature 7 × 7 surface. In going from high-T 7 × 7 surface to high-T 1 × 1 surface, no essential changes in the surface-state peaks have been found to occur.

Photoelectron diffraction and low energy electron diffraction studies of Cs, K/si(001) surfaces

Abstract X-ray photoelectron diffraction patterns of Cs 3d core levels for the full-Cs-coverage Si(001)-2 × 1-Cs surface have been measured and analyzed kinematically. It is found from the analysis that one monolayer of Cs, i.e., Cs/surface-Si ratio of unity, is present over the substrate forming a double-layer (upper and lower) array of atoms. The arrangement of Cs atoms in the double layer is essentially the same as the K double layer for the Si(001)2 × 1-K surface. New surface orders are reported that can be formed by the deposition of Cs or K atoms onto an annealed Si(001) substrate.

Angle-scanned photoelectron diffraction

A brief survey is given on the current state-of-the-art of this surface structural technique based on photoelectron spectroscopy, with particular emphasis on the progress that has been made recently by routinely measuring full-hemispherical intensity distributions. We limit the discussion to the photoelectron forward focusing regime, which is attained at electron kinetic energies of a few hundred eV. Surface bond directions are directly revealed as pronounced maxima in the angular distributions from subsurface atoms, while characteristic interference features are observed for surface species. For both cases the dependence on the atomic type is weak enough so that these features provide a fingerprint of the local bonding geometry. For surface and near-surface species, this may then serve as a starting point for a structure refinement using single-scattering cluster calculations. Selected examples are given for illustrating these procedures.

Structure analysis of the single-domain Si(111)4 × 1-In surface by μ-probe Auger electron diffraction and μ-probe reflection high energy electron diffraction

Abstract A single-domain Si(111)4 × 1-In surface has been studied by μ-probe reflection high-energy electron diffraction (RHEED) to elucidate the symmetry of the 4 × 1 surface. Azimuthal diffraction patterns of In MNN Auger electron have been obtained by a μ-probe Auger electron diffraction (AED) apparatus from the single-domain Si(111)4 × 1-In surface. On the basis of information from scanning tunneling microscopy [J. Microsc. 152 (1988) 727] and under the assumption that the 4 × 1 surface is composed of In-overlayers, the μ-probe AED patterns were kinematically analyzed to reach a concrete model of indium arrangement.

Low energy electron diffraction and X-ray photoelectron diffraction study of the Cs/Si(001) surface: dependence on Cs coverage

Cs adsorption on a wide-terrace single-domain Si(001) surface has been studied by low-energy electron diffraction (LEED) and X-ray photoelectron diffraction (XPD) as a function of Cs coverage (θ) and substrate temperature (TS). For TSs of ~ 110 and ~ 320 K, several surface periodicities are found which have not been reported before for this system. Azimuthal Cs3d XPD patterns have been measured for most of the ordered surfaces. An XPD structure analysis is made for a streak × 3 surface at θ = 16 ML, in which a dilute arrangement of Cs atoms is deduced. An XPD structure analysis is made for the surfaces at θ = 13 ML taking into account a reversible transition between 2 × 6 and 2 × 3 for TSs of ∼ 110 and ∼ 320 K, respectively. A Cs dimer model is deduced in which a modulation of atomic positions into a 2 × 6 surface is averaged in the 2 × 3 surface but is fixed in a regular way in the 2 × 6 surface.

Soft X-Ray Absorption Spectra of Some Metal Chlorides

The Cl - L 23 absorption spectra of thin films of CuCl, ZnCl 2 , CdCl 2 , PbCl 2 , MnCl 2 , FeCl 2 , CoCl 2 , NiCl 2 , MgCl 2 , CaCl 2 , SrCl 2 , and BaCl 2 have been measured by the photographic method using synchrotron radiation from a 1.3 Bev electron synchrotron as a soft X-ray source. In all materials studied, other than CaCl 2 , SrCl 2 , and BaCl 2 , the absorption spectra near the threshold show absorption bands probably due to the creation of excitons with holes in the 2 p level of chlorine. The intense and broad absorption continuum beginning around 211 eV is observed in all materials studied. This absorption is assigned to the atomic excitation of Cl - ions. Discussion is given about the profile of each spectrum.

Initial stage growth of In and A1 on a single-domain Si(001)2 × 1 surface

Abstract Initial stage growth of In and A1 on a wide-terrace single-domain Si(001)2 × 1 surface has been studied by low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy. Several submonolayer phases that were not reported on double-domain Si(001)2 × 1 substrates are observed, in addition to those already reported. The resulting sequences of two-dimensional (2D) phases for In and A1 coverages of ≤ 0.5 ML can be interpreted based on an order-disorder transition of arrays of 1D metal-dimer chains. The results show close resemblance to the initial growth of Ga on Si(001) and thus indicate that there is a general mode of growth for the Group-III metals on a Si(001)2 × 1 surface below 0.5 ML. Growth for coverages greater than 0.5 ML and the onset of 3D growth are also discussed.

Photoelectron and inverse photoelectron spectroscopy studies of the Si(111)3 × 3-Sb surface

Abstract Angle-resolved ultraviolet photoelectron spectra and momentum (k)-resolved inverse photo-electron spectra have been measured for the Si (111) 3 × 3 - Sb surface. It has been found that at least two filled-surface-state bands exist on the 3 × 3 - Sb surface and that the 3 × 3 - Sb surface is semiconducting with a large band gap between the filled- and empty-surface-state bands. The absence of dangling bonds in this surface is suggested from results of hydrogen exposure. These results are discussed in connection with the surface electronic structures expected for a recently proposed trimer model.