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Addition of rather large amounts of Cu in a-As 2 S 3 and a-As 2 Se 3 , induces suppression of the normally observed photodarkening. We have used X-ray photoelectron spectroscopy (XPS) to examine the effects on the electronic structure of the incorporation of increasing amounts of Cu atoms into the a-As 2 S 3 and a-As 2 Se 3 lattices. We show that initially the addition of Cu affects the environment of the elements in the amorphous chalcogenide glasses, without at the same time suppressing the photodarkening. On the other hand, as more Cu atoms are introduced in the network, Cu aggregates form; the initial chalcogenide electronic structure tends to be restored; and the photodarkening is suppressed.

X-ray photoelectron and emission spectroscopies have been used to study the electronic structure of Cux(As2S3)1−x and Cux(As2Se3)1−x compounds across the range where the amount of Cu in the sample strongly affects the photodarkening (PD). Shifts of the As 3d, S 2p and Se 3d core level energies in Cu-containing samples indicate Cu bonding to As as well as to the chalcogen atoms. These shifts are largest in the selenide compounds. Low-temperature (∼0.4 K) anomalies and vectoral photoinduced effects are found to be much less affected by the Cu addition than is the PD.

An investigation by X-ray photoelectron spectroscopy (XPS) of adhesion mechanisms of a-Si:H films on stainless steel substrates after hydrogen (H2), nitrogen (N2) and ammonia (NH3) plasma treatments of the surface is presented. It is shown that adhesion is increased by N2 treatment. This effect is related to chemical bonding states at the interface. The improvement is attributed to the formation of silicon nitride at the interface and to the existence of Fe–Fe metallic bonds which contribute to a hardening of the substrate.

Polymer-like hydrogenated amorphous carbon (a-C:H) films containing increasing concentrations of Si atoms (up to 12 at.%) have been grown using a dual-mode plasma (microwave and radiofrequency) plasma enhanced chemical vapor deposition reactor with low ion energies. X-ray emission and X-ray photoelectron spectroscopies (giving respectively Si 3p states and the total valence band states) have been used to probe the electronic structure. Complementary information on the local bonding have been obtained from the Si 2p and C 1s core levels. These results show that the Si bonding environments are consistent with Si–C4 units. The influence of the tetrahedrally bonded Si atoms on the C atom local environment is basically explained by a topological effect rather than a change in the C hybridization.

The local order in Plasma-Enhanced Chemical Vapor Deposition (PECVD) N-rich a-SiN x :H films is shown to depend strongly on the H bonding configuration. The SiH bonding affects the SiN lattice vibration, giving a shoulder at 1020 cm −1 , and shifts the Si3p - N2p peak position in the valence band distribution towards lower binding energies.

The density of valence states of amorphous hydrogenated silicon-nickel a-Si 1−y Ni y :H alloys has been experimentally investigated by soft X-ray emission (SXS) and optical spectroscopies. By SXS, partial Si 3p and Ni 3d valence states are obtained on a common energy scale referred to the Fermi level. Our results show that, as the Ni content is increased, the uppermost valence band changes from Si 3p to hybridized Si 3p-Ni 3d states, leading to a finite density of states at the Fermi level. The results are discussed in relation to optical measurements performed on samples deposited at the same time.

In order to better understand B(CH3)3 doping effect on a-Si:H characteristics, the local Si bonding have been studied by XPS in B(CH3)3 or B2H6 doped a-Si:H and a-Si1-xCx:H respectively. The results have been correlated to ellipsometry measurements. Boron is found to enhance the incorporation of C in the films; B(CH3)3 largely changes the film growth and the optical properties of the material. These effects can not be attributed to individual B and C effects.

The optical properties of evaporated amorphous GeSe 2 films have been determined before and after annealing by transmission and photothermal deflection spectroscopy measurements. The results are analyzed together with those of X-ray photoemission and X-ray diffraction experimemts. The annealing effects are related to changes in medium-range order. The low-energy optical absorption shows a defect state density varying with deposition conditions and annealing

The paper deals with the interpretation of fundamental, combination, and first overtone vibration signals of OH groups and H2O on silica gel. A signal at 4425 cm−1 is assigned to vibrations of free OH groups, while a signal at 4505 cm−1 is attributed to vibrations of the sum of all OH groups, independently of their types. A molar absorption coefficient of H2O signal at 5235 cm−1 was determined. Fundamental bands of H2O and OH groups in the 3100–3800 cm−1 range cannot be separated and interpreted quantitatively.

Electronic structure and properties have been compared for amorphous germanium selenide films with compositions near GeSe 2 to GeSe 3 , and prepared by either plasma-enhanced chemical vapour deposition (PECVD) of GeH 4 and H 2 Se mixtures, or by thermal evaporation of bulk germanium selenide compounds. X-ray photoelectron spectroscopy (XPS) is used in conjunction with photo- and dark conductivity measurements. XPS spectra from Ge 3d and Se 3d core levels, and of the valence band, reveal no significant difference in electronic structure, but the electrical measurements point to a different position of the Fermi level in the two types of material. It is suggested that PECVD produces a distribution of localized gap states which pushes the Fermi level closer to the transport band.

The irreversible changes in conductivity occurring in evaporated amorphous Ge films just after deposition and during annealing are investigated in detail. Their analysis leads to a model for the structural relaxation of real amorphous networks. Electron diffraction and electron microscope experiments provide additional information on annealing effects and crystallization processes.

The results of a detailed study of the effects of disorder and defects on the core level and valence band distributions in amorphous GaAs by X-ray photoelectron spectroscopy, are discussed and compared to those of similar experiments on amorphous Ge. We analyse the differences between the compound and the element in terms of medium-rangedisorder and we study the annealing effects. In the GaAs case, we show evidence for states associated with AsAs wrong bonds, in agreement with theoretical predictions.

As-deposited and annealed flash-evaporated amorphous InP films are studied by electron diffraction experiments and by optical and d.c. conductivity measurements. We show that wrong bonds are not introduced by odd-membered rings but are due to the particular deposition process. We discuss the influence of the different defects, both structural and chemical, on the electron density of states in comparison with amorphous GaP.

The local environment of P and In in amorphous InP has been investigated by EXAFS at both K edges. EXAFS spectra are fitted by a two shell model with two types of neighbours, which suggest the presence of partial chemical disorder in this material.

The optical absorption edge of evaporated a-Ge films and flash-evaporated a-GaAs films is accurately determined as a function of annealing, down to 0.5 eV, by combining spectrophotometric and photothermal deflection spectroscopy measurements. The results are compared and interpreted in terms of disorder and defects. A dangling bond contribution is clearly observed in annealed a-Ge. The defect states associated with dangling bonds and wrong bonds in stoichiometric and As-rich a-GaAs are discussed.

An e.p.r. study on stoichiometric and As-rich amorphous GaAs films prepared by flash-evaporation shows the presence of two different paramagnetic defects in the 10 18 cm −3 concentration range. The dominant defect in stoichiometric a-GaAs, ascribed to the As dangling bond, increases in concentration during crystallization. The unidentified defect in As-rich films anneals out at the crystallization. No signal which could be associated with the As antisite defect is detected in these samples.

A simple model is presented which interprets conductivity variations due to crystallization in amorphous layers and allows the determination of the growth rate of crystallization. The validity of this model is demonstrated in the case of germanium.

Soft X-ray spectroscopy (SXS) and X-ray induced photoelectron spectroscopy (XPS) measurements have been performed on amorphous InP samples prepared by flash evaporation, comparatively to crystalline InP. SXS results reveal striking differences in the 3p states of the valence band distribution of a-InP as compared to c-InP. The presence of a partial chemical disorder in a-InP is deduced from XPS measurements.

The electronic density of states of flash-evaporated amorphous In 1−x P x films, with x > 0.5, is investigated in detail by X-ray photoelectron spectroscopy and by combined optical and photothermal deflection measurements. The results are analyzed in terms of structural and chemical defects, in relation with the predictions of recent theoretical work.

The results of EXAFS, optical and electrical measurements performed on amorphous GaAs and GaP films as a function of deposition conditions and annealing are discussed and compared. In the case of GaP, the existence of wrong bonds is suggested by the analysis of EXAFS data as well as by the behavior of the optical properties near the absorption edge and of the conductivity at high temperatures.

The temperature dependence of the electrical conductivity, piezoresistance and thermopower as well as optical absorption have been measured on amorphous carbon films deposited by electron beam evaporation on silica substrates. In as-deposited films transport properties and optical absorption imply the existence of an energy pseudo-gap of ⪆ 0.65 eV. All the results lead to a structural model in which the carbon atoms are bound together by intimately intermixed trigonal and tetrahedral links. Annealing above 750°K gives the films transport and optical properties quite similar to those of polycrystalline graphite and also induces optical absorption peaks situated at 7–8 eV characteristic for diamond only. It is therefore concluded that annealed films consist of tiny islands with alternatively graphite and diamond structure.

The effects of alloying on the density of states near the band edges and in the pseudo-gap in a-Si 1−x Ge x :H alloys with O ⩽ x ⩽ 1 prepared under identical conditions by glow discharge decomposition of SiH 4 /(GeH 4 + H 2 ) mixtures, have been investigated by combining photothermal deflection spectroscopy and soft X-ray spectroscopy. A tentative model for defect-related states is deduced from the data.

An XPS study of the Si 2p and N1s core levels and of the valence band of a-SiN x :H samples prepared by 254 nm Hg photo CVD is presented. From the Si 2p study, various SiN x configurations are evidenced, the SiN 4 unit being predominant for x ⪆1 . The N1s core level modifications are interpreted in terms of H n NSi m configurations. At the top of the valence band, the Si 3p states from SiSi bonds are progressively replaced by N 2p states due to SiN bonds.