The electronic structure of ZnO and its defects, which include intrinsic point defects and their complexes, have been calculated using full-potential linear Muffin-tin orbital method. According to our calculation data, the positions of the defect state levels have been determined in the energy band of ZnO. Based on the results above, we analysis the mechanism of the absorption and emission spectra of ZnO and discuss the effects of the electronic structure of complete ZnO and its defects on the spectral properties.

The native point defect states in ZnO have been calculated by using a full-potential linear muffin-tin orbital method. The results show that Zn vacancy and O interstitial produce the shallow acceptor levels above the valence band. The O vacancy produces a deep donor level, while Zn interstitial produces a shallow donor level, both below the conduction band. The Zn interstitial is the main factor which induces the native n-type conductivity in ZnO.

First-principle calculations are performed on ZnO:VO, ZnO:VZn and ZnO:ZnI using a FP–LMTO (full potential linear muffin-tin orbital) method. The results prove that the ZnI is the dominant donor in ZnO, and VZn, a shallow acceptor, while VO is a deep donor.

Soft X-ray synchrotron radiation photoemission (SRPES) and XPS were used to study the interaction of oxygen with Gd–Ni composite and Gd cluster films grown on Ni(110) surface. Different oxidation manners were found for the two kinds of films. Over the Gd–Ni composite film, the adsorption of oxygen resulted in the segregation and oxidation of Gd component, and chemisorbed O− and lattice oxygen were detected. For the Gd cluster film, with the increase of oxygen exposure the oxidation states of Gd were developed between the two peaks of the Gd4f double-peak at the expense of attenuation of HBE peak. Only one O1s XPS peak at 529.6 eV was detected in the range of 0–50 L exposure.

The interaction of ultrathin Mg and MgOx films with the GaAs(100) semiconductor substrate was investigated using synchrotron radiation photoemission. The results showed that strong interaction existed between Mg and GaAs leading to the formation of an interface more than 11 A, while negligible interaction and interdiffusion took place between the MgOx overlayer and the substrate. Different Mg:O-2 ratio during the deposition gave rise to the formation of MgOx with different compositions and properties. (C) 1999 Elsevier Science B.V. All rights reserved.

An organic sulfide, CH3CSNH2 treated sulfur-passivated GaAs(100), has been studied using synchrotron radiation photo-emission spectroscopy (SRPES), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The SRPES and AES measurements show that the treatment removes the GaAs surface oxide layer and forms sulfides of Ga and As on the surface. The thermal stability and surface structure of the passivated samples at different temperatures have also been studied. We found that the surface sulfides are also gradually removed and a clean, ordered and thus Fermi level unpinning surface can finally be achieved. Surface restructuring can be observed from the GaAs(100)–S (2×1) pattern between 260 and 450°C to the (4×1) pattern without S between 460 and 550°C.

Contradictory results are obtained when Gd is deposited on S–GaP(100) and GaAs(100) substrates, respectively. The Gd4f spectra from Gd/S–GaP show single peaks with binding energy 8.3 eV at a thickness of 0.9 nm. However, the Gd4f spectra from Gd/GaAs evolve from a narrow peak into a two-featured structure with an increment of Gd. At a thickness of 2.33 nm, one feature centers at 10.3 eV binding energy, and another at 8.0 eV. We confidently exclude the contribution of contamination in these unexpected results and a new phase is supposed.