In4d Core Levels Research Articles

Electron spectroscopy studies of surface In–Ag alloy formation on the tungsten surface

XPS and UPS investigations of ultrathin films of In/Ag and Ag/In, deposited onto the W(1 1 0) surface in the ultrahigh vacuum conditions have been performed. Indium and silver films were formed by “in-situ” evaporation on W(1 1 0) substrate. XPS and UPS studies have been performed by means of SCIENTA ESCA200 instrument. The changes of In4d core-level and Ag4d valence band emissions with increasing Ag and In coverage were monitored to observe the energy shift and shape of the spin–orbit doublet of In4d and Ag4d lines in the Ag/In/W and In/Ag/W systems. UPS (HeI and HeII) measurements were supported by XPS AlK α measurements of In3d and W4p levels, as well as by investigations of Ag3d levels. XPS and UPS data allowed to evaluate the coverage and make conclusions concerning intermixing and surface alloying in the In/Ag/W and Ag/In/W systems. W(1 1 0) substrate can be cleaned after each deposition by thermal desorption and no alloying in the In/W and Ag/W systems is observed.

Morphology and surface electronic structure of MBE grown InN

The morphology and surface electronic structure of indium nitride films grown by plasma-induced molecular beam epitaxy have been studied using atomic force microscopy as well as X-ray and ultraviolet photoelectron spectroscopy. Valence band and In4d core level spectra were measured as a function of excitation energy (He I, He II and AlK α radiation) on samples with minimised exposure to ambient conditions after growth (30 s). A work function of 4.1 eV was determined and the onset of the valence band is located 1.6 eV below the Fermi level which is a strong indication of the already discovered electron accumulation at InN surfaces. In addition, the theoretically predicted InN valence states were observed. At the outermost InN surface the In4d level seems to consist of two components, where the existence of a metallic phase can be ruled out by a comparison with sputtered InN samples and measurements performed on an indium foil.

Photoemission and Low-Energy Electron-Diffraction Studies of α-Sn Growth on InSb Surfaces

In this paper we present an experimental study of the growth morphology and of the electronic properties of Sn growth on polar InSb (111) A- and B-type surfaces, and on the InSb (100)-c(2 × 8) surface, the valence band and In-4d core level evolution as a function of Sn coverage have been measured by high-resolution ultra-violet (UV) photoemission spectroscopy, while the surface symmetry has been monitored by low-energy electron-diffraction. Clear (2 × 1)-reconstruction has been singled out on the (100) surface, while a (1 × 1)-Sn(111) layer has been obtained on the (111)-oriented substrates, and In interdiffusion has been observed into the Sn matrix.

Valence band and In-4d core level photoemission study of de-capped and ion-bombarded-annealed InAs(0 0 1) epitaxial surfaces

The (4 × 2) epitaxial InAs(0 0 1) surface grown by molecular beam epitaxy and subjected to different surface treatments, namely amorphous As-de-capping and ion-bombardment annealing (IBA), is investigated by high-resolution angular-resolved UV photoelectron spectroscopy. Both treatments produce a semiconducting surface, ruling out the presence of metallic In aggregates. Binding energy shifts of 0.2–0.3 eV are measured for the valence-band levels of the IBA surface with respect to the de-capped surface, implying an important influence of the surface treatment on the subsurface region. The line-shape of the In-4d core levels, which consists of two different In-related surface doublets, is discussed in view of the recently proposed structural models based on dimers formation.

Electron accumulation layer on clean In-terminated InAs(0 0 1)(4×2)-c(8×2) surface

We have investigated clean In-terminated InAs(001)(4×2)-c(8×2) surface by LEED, STM and high-resolution core-level and valence band (VB) spectroscopies. The In4d and As3d core levels showed the presence of chemically shifted components. The decomposition of In4d core level exhibited a new surface component located close to that of free indium metal. This indicates that the origin of the electron emission at the Fermi level measured in the VB spectra is probably due to the free In charge. STM measurements showed a uniform distribution of charge on the In-rows, which are highly ordered over large areas of the surface.

α-Sn pseudomorphic growth on InSb (111) and ( [formula omitted]) surfaces: a high-resolution photoemission study

The Sn–InSb interface and α-Sn ultrathin film formation on the sputter-annealed clean A- and B-type InSb(111) surfaces are studied by high-resolution UV photoelectron spectroscopy. The valence band and In-4d core levels, along with the relieving of the clean surface reconstruction, suggest a model for the interface formation at low coverage. At higher Sn thickness a good-quality α-Sn(111)-(1×1) layer is formed, and the In-4d and Sn-4d core-level analysis shows a slight In interdiffusion present on both substrates.

Atomic Surface Structure of MOVPE-Grown InP(001)

In this study soft X-ray photoemission spectroscopy (SXPS) and scanning tunneling microscopy (STM) were used to investigate the microscopic structure of the P-rich so-called (2×1) reconstruction of InP(001). The samples were homoepitaxially grown in a commercial MOVPE reactor, transferred to ultra high vacuum (UHV), and then transported to separate UHV analysis chambers. Electron diffraction patterns of the samples taken after transfer show a (2×1)/(2×2) periodicity with streaks in the [1-10] direction. STM images display rows along the [110] direction showing a twofold periodicity. Consistent with SXPS spectra of the P2p and In4d core levels the structure can be explained by a fractional monolayer of P-dimers adsorbed on a complete second layer of P. The P-dimers are arranged in local (2×2)/c(2×2)/c(4×2) structures showing a lack of long-range ordering.

Photoelectron Diffraction Investigation of Strained InGaAs Grown on (001) GaAs

We have performed Soft X-Ray Photoelectron Diffraction measurents, at the Ga3d, As3d and In4d core levels, to study the effects of strain on InGaAs grown on (001) GaAs. Polar and azimuthal scans have been recorded and compared with Single Scattering Cluster Calculations. A good agreement is obtained between theory and experiment indicating that the lattice expands in the growth direction as predicted by the elastic theory.

A STUDY OF SULFIDE TREATED InSb(111) SURFACES

Auger electron spectroscopy (AES), X-ray photoelectron spectroscop (XPS) and ultraviolet photoelectron spectroscopy (UPS) have been used to study the InSb(lll) surfaces treated with (NH4)O2Sx. It is found that after the sulfide treatment, the sample surfaces are covered by a thin overlayer of sulfide (8?), which prevents the sample surface from oxidization and carbon contamination in the air. XPS and UPS results show that S atoms bond to both Sb atoms and In atoms on the sample surfaces. Sb-S bonding peaks in the Sb3d spectra exhibit a core level shift of 1.9eV, the bonding of S to In atoms causes an In4d core level shift of 0.6-0.7eV. A thermal annealing at 350℃ gives rise to the decomposition of Sb-S bonding and the evaporation Sb atoms from the sample surfaces. In-S bonding can not be decomposed completely by annealing up to 500℃ and a small amount of S atoms remains on the sample surfaces in the form of indium sulfide.