Valence and core state modifications in Pt3Ti

XPS data for the valence band, the Pt 4? states, and the Ti 2p states are presented for the intermetallic Pt₃Ti. Relative to the Pt valence band, the Pt₃Ti band shows a decrease in the density of states just below the Fermi level and a shift of the centroid to higher (binding) energy. Ti 2p and Pt 4? binding energies showed relatively large shifts with respect to the pure metals. These changes in the valence band density of states and core level binding energies are interpreted as arising from hybridization of the d-orbitals in both metals to form strong intermetallic bonds.     

Energy band structure and refractive properties of LiRbSO4 crystals

The energy band structure of mechanically free and compressed LiRbSO₄ single crystals is investigated. It is established that the top of the valence band is located at the D point of the Brillouin zone [k = (0.5, 0.5, 0)], the bottom of the conduction band lies at the Γ point, and the minimum direct band gap E _g is equal to 5.20 eV. The bottom of the conduction band is predominantly formed by the Li s, Li p, Rb s, and Rb p states hybridized with the S p and O p antibonding states. The pressure coefficients corresponding to the energies of the valence and conduction band states and the band gap E _g are determined, and the pressure dependences of the refractive indices n _i are analyzed.     

Electronic structure of black phosphorus studied by X-ray photoelectron spectroscopy

The X-ray photoelectron spectrum of black phosphorus has been measured for the first time. The features in the valence band spectrum are found to be in good agreement with those of the valence state density recently calculated on the basis of a pseudopotential method. The 2s and 2p core spectrum of black phosphorus is also discussed.     

Photoemission studies of single crystals of titanium carbide

The electron distribution in the valence band from single crystals of titanium carbide has been studied by photoelectron spectroscopy with photon energies h?ω = 16.8, 21.2, 40.8 and 1486.6 eV. The most conspicious feature of the electron distribution curves for TiC is a hybridization between the titanium 3d and carbon 2p states at ca. 3–4-eV binding energy, and a single carbon 2s band at ca. 10 eV. By taking into account the strong symmetry and energy dependence of the photoionization crosssections, as well as the surface sensitivity, we have identified strong emission from a carbon 2p band at ? 2.9-eV energy. Our results are compared with several recent energy band structure calculations and other experimental data. Results from pure titanium, which have been used for reference purposes, are also presented.The valence band from single crystals of titanium carbide have been studied by means of photoelectron spectroscopy, with photon energies ranging from 16.8 to 1486.6 eV.By taking into account effects such as the symmetry and energy dependence of the photoionization cross-sections and surface sensitivity, we have found the valence band of titanium carbide to consist of two peaks. The upper part of the valence band at 3–4 eV below the Fermi level consists of a hybridization between Ti 3d and C 2p states. The C 2p states observed in our spectra were mainly excited from a band about 2.9 eV below the Fermi level. The APW^5–9, MAPW¹⁰ and EPM¹¹ band structure calculations predict a flat band of p-character between the symmetry points X′₄ and K₃, most likely responsible for the majority of C 2p excitations observed. The C 2s states, on the other hand, form a single band centered around ?10.4 eV.The results obtained are consistent with several recent energy band structure calculations^{5–11, 13} that predict a combined bonding of covalent, ionic and metallic nature.     

Electronic structure of PbI2 from photoelectron spectra and the exciton problem

The valence band density of states for PbI₂ is determined from X-ray and u.v. induced photoelectron spectra. It is shown that the band derived from Pb 6s states is at 8 eV binding energy and not at the top of the valence bands as suggested by band structure and charge density calculations. A rigid shift in the predominantly iodine 5p derived bands to lower binding energy brings the band structure calculations into essential agreement with experiment. Pb 5d core level binding energies determined here are used to derive core level exciton energies of 0.7 eV from published reflectivity spectra.     

Electronic band structure of In2S3 and CdIn2S4 semiconductor spinels from the data of x-ray spectroscopy and theoretical calculations

The electronic band structure of the chalcogenide spinels In₂S₃ and CdIn₂S₄ has been studied using the FEFF8 program. It is shown that the valence band top is formed by the S p states mixed with the In s and In p states for In₂S₃ or with the Cd s, Cd p, In s, and In p states for CdIn₂S₄. Compared to In₂S₃, the presence of Cd atoms in the nearest environment of S atoms in CdIn₂S₄ does not considerably affect the electronic band structure. In CdIn₂S₄ the Cd 4d states, as well as the In 4d states, form a narrow localized band shifted deep into the valence band. The theoretical results are in good agreement with the experimental x-ray photoelectron and x-ray spectra.     

Valence-level structure of phosphides of 3d-metals on the basis of XRS and ESCA data

For the first time, comprehensive X-ray spectroscopic and X-ray photoelectron data have been obtained on the energy spectra of valence electrons in phosphides of the transition metal series: TiP, CrP, MnP, FeP, NiP.Analysis of the experimental data on the electronic structure of phosphides of 3d-metals in the TiPNiP series indicates that the mechanism of interaction of the M 3d-states occurring near the top of the valence band with the s,p-states of phosphorus in the following sub-bands resides in the latter being induced near the d-sub-band as a result of the M 3d—P 3s,p interaction with the density maximum of the nearest P 3p-states being oppositely shifted as the number of d-electrons of the metal increases. Analysis of X-ray spectroscopic and X-ray photoelectron data on phosphides of transition metals along with those of metals of groups I(Cu, Ag) and II(Zn, Cd), and comparison of these data with the results of similar studies involving sulphides and silicides of the same metals indicate that the occupancy and the associated position of the d-shell of the metal within the valence band are the determining factors as far as the mutual arrangement of energy sub-bands and the symmetry of respective states are concerned.     

Electronic structure of SiO2(111) thin film

The electronic structure of (111) surface of β-crystobalite is investigat ed using the empirical tight binding method. Our calculations identify surface states in the conduction band, band gap and valence band. The surface state formed from silicon-s and p_z orbitals, which is believed to account for the structure in the O K excitation spectra, lies in the band gap. It is seen that oxygen adsorption on the surface removes surface states and gives rise to a sharp peak at about — 3.8 eV below the valence band edge.     

Comparison of site-specific valence band densities of states determined from Auger spectra and XPS-determined valence band spectra in GeS (001) and GeSe (001)

Auger lineshapes of the Ge M₁M_4,5V and M₃M_4,5V and Se _M1M_4,5V transitions in GeS (001) and GeSe (001) are measured and compared to XPS valence band spectra. Distortions in both types of spectra due to inelastic scattering, analyzer and source broadening, and core level lifetime broadening are removed by deconvolution techniques. The valence band consists of three main peaks at ?2 eV, ?8 eV, and ?13 eV. There is excellent agreement of peak positions in AES and XPS spectra. The Auger lineshapes can be interpreted in terms of site-specific densities of states. They indicate that the states at ～?8 eV and at ～?13 eV are associated with the cation and anion sites respectively. The bonding p-like states at the top of the valence band have both cation and anion character. The Auger lineshapes indicate that the states closest to the valence band maximum are preferentially associated with Ge.     

Investigation of the band structure of germanium chalcogenides by means of photoelectron spectroscopy

The valence band photoelectron spectra of amorphous GeS, GeSe and GeTe have been measured. The ultraviolet and X-ray excited spectra show three bands associated with bonding p-states, anti-bonding and bonding s-states, respectively. In the ultraviolet photoemission spectra the p-band shows a pronounced fine structure. Features of the valence band density of states estimated on the basis of a tightbinding model are in reasonable agreement with experiment. Some problems connected with the extension of the ionicity concept of Phillips and van Vechten to the IV–VI compounds are discussed.     

Electronic structures of MRhO2, MRh2O4, RhMO4 and Rh2MO6 on the basis of X-ray spectroscopy and ESCA data

X-ray O Kα, Rh Mγ and a series of M Lα emission spectra, ESCA spectra of the valence and inner levels, and O K and Rh M_III quantum-yield spectra for X-ray photoemission of the rhodium double oxides MRhO₂ (M = Li, Na, K), MRh₂ O₄ (M = Be, Mg, Ca, Sr, Ba, Co, Ni, Cu, Zn, Cd, Pb), RhMO₄ (M = V, Nb, Ta) and Rh₂MO₆ (M = Mo, W) have been measured and the dependence of electronic structure on the metal M analysed. For all compounds the inner part of the valence band corresponds to O 2p_σ + O 2p_π + Rh 4d states, while the outer part corresponds to Rh 4d. The valence band is separated from the conduction band by a narrow gap of width less than 1 eV. The first empty band, near the bottom of the conduction band, is formed by Rh 4d states, followed by a band due to vacant O 2p states.     

Cluster model calculations for Cl chemisorbed Si and Ge (111) surfaces by iterative extended Hückel theory

Local densities of states are calculated by use of a cluster model. Resonant states due to Cl 3p orbitals appears in the valence band. The calculated energy-splittings between non-bonding p_x(p_y) and bonding p_z orbitals agree well with the observed ones.     

The effect of transition probability on the shape of X-ray photoelectron spectra of diamond and silicon

X-ray photoelectron spectra of valence bands in diamond and silicon have been calculated. It is shown that the probability of electron excitation from s-states is higher than that from p-states. The density of the electron states in the valence band of these crystals differs markedly from the energy distribution of photoelectrons.     

Separation of the partial s- and p-densities of valence states of ZnO from UPS-measurements

UPS-spectra of the cleaved (0001) Zn and (000$\text{1}$) O surfaces of ZnO are taken at hv = 16.8, 21.2, 26.9, and 40.8 eV. Two maxima in the spectra at constant final energy are ascribed to high densities of conduction band states. Using the hv-dependence of the valence band emission, the partial s- and p-densities of states are separated. They yield similar excitation probabilities for Zn-4s-, 3d-, and O-2p-electrons.     

A study by XPS and XRS of the participation in chemical bonding of the 3d electrons of copper,zinc and gallium

The participation of 3d electrons in chemical bonds and their part in the formation of valence bands was studied by X-ray photoelectron- and X-ray-spectroscopy for Cu, Zn and Ga phosphides, sulphides and oxides. Incomplete screening of (n + 1)s,p electrons through the nd shell leads to non-systematic changes of orbital energies and radii of the valence electrons in the first, second and third Group elements. It is reflected in the electronic structure of the respective compounds. A qualitative interpretation of XPS and XRS data for Cu, Zn, Ga phosphides is given. Possible reasons for phosphorus s band splitting for zinc and copper phosphides are considered. The interaction of 3d metal states and 3s, p third Period element states considerably affects the valence band of compounds, and this interaction should be taken into account when considering electronic structures of Cu, Zn and Ga compounds.     

Direct observation of occupied gap states in amorphous Si1-xGex: H alloys by SXS

SiKβ emission band have been analysed from a-Si_1-xGe_x: H alloys for Ge concentrations varying from 0.05 to 0.60. Localized states with p character are observed in the pseudo-gap near the valence band edge.     

Electronic structure of CsAu

X-ray photoemission spectra of CsAu prepared in vacuum are in good agreement with the ionic character expected for this material. The Cs 5p doublet lies well below flat Au 5d bands. The Au 6s valence band is located somewhat closer to the 5d states than recent band structure calculations indicate. The charge transfer to gold is in the range 0.6 to 0.8 electrons.     

Self-consistent numerical solutions of p-type inversion layers in silicon mos devices

We present a self-consistent numerical calculation to study the energy of the subbands of holes on p-type inversion layers in silicon MOS devices. The variation of the masses with the concentration of carriers is considered self-consistently, taking into account the non-parabolicity and anisotropy of the valence band. These properties are mandatory on the behaviour of the excited states giving opposite trends for p-type and n-type channels.     

Electronic structure of the CuBS2 crystal

The band structure and spectra of the total and projected densities of states of a new crystal of the chalcopyrite family, namely, CuBS₂, have been calculated in terms of the density functional theory. It has been found that the crystal is a pseudo-direct-band-gap semiconductor, and the best theoretical estimate of the optical band gap is 3.44 eV. The upper valence band of the CuBS₂ crystal basically consists of the contributions from the p states of S atoms and the d states of Cu atoms. The crystal splitting is 0.2 eV. The bottom of the conduction band is basically formed by the sp states of boron and sulfur atoms with an admixture of the s states of copper atoms.     

Interpretation of far-infrared absorption spectra in germanium

The high resolution far-infrared absorption spectra of free excitons in germanium are analyzed for the first time using a model which accurately includes both the anisotropy of the valence and condition bands and the degeneracy of the valence band. The observed structure is in good agreement with the calculated transitions between the anisotropy split ground state and the various p-like excited states.