Lu Er-Dong

A FP–LMTO study on the native shallow donor in ZnO

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

A novel sulfur-passivation method and magnetic overlayers on passivated III–V semiconductor surface

Abstract A sulfur passivation method for GaAs, CH3CSNH2 treatment has been developed. It is quite effective for removing the surface oxide layer and forming the sulfide passivation layer on GaAs surface, with sulfur atoms bound with Ga and As atoms. After being annealed, a stable sulfur passivation layer is formed. The enhancement of PL intensity reveals the reduction of surface non-radiative recombination and the density of surface states. Moreover, the investigation has been made for the role of S-passivation on interfacial interaction between magnetic overlayer and GaAs. The interdiffusion of As, Ga into overlayer is effectively inhibited, and the magnetization of Fe overlayers is enhanced. In addition, a relationship has been found between the surface chemical structure of the substrates and the magnetic property of overlayers.

PHOTOEMISSION-STUDIES OF K-PROMOTED NITRIDATION OF INP(100) SURFACE USING SYNCHROTRON-RADIATION

The effect of molecular nitrogen exposure on the surfaces of InP(100) modified by potassium overlayers is investigated by core-level and valence-band photoemission spectroscopy using Synchrotron radiation. In comparison with InP(110) surface, we found the promotion is much stronger for InP(100) surface due to the central role of surface defects in the promotion; furthermore, in contrast with K-promoted oxidation of InP(100) where the bonding is observed between indium and oxygen, indium atoms did not react directly with nitrogen atoms during the K-promoted nitridation of InP(100).

Effect of Growth Temperature on the Band Lineup of Ge/CdTe(111) Polar Interfaces

By using synchrotron radiation photoelectron spectroscopy, the band lineup of Ge/CdTe(111) interfaces grown at different temperatures have been measured. Experimental studies show that the valence band offset of Ge/CdTe(111) interface grown at room temperature is 0.88?0.1 eV, which agrees well with previously reported value. While as for the interface grown at 280?C, an obvious reduction of valence band offsets is observed and attributed to the effect of different interface dipole.

A new method to enhance the magnetism of Fe overlayer on GaAs(100): sulfur passivation using CH3CSNH2

Ferromagnetic resonance (FMR) has been used to investigat the magnetism of Fe overlayer on S-passivated GaAs(100) pretreated by CH3CSNH2. Comparing with the magnetism of Fe overlayer on clean GaAs(100), we find that sulfur passivation can prevent As diffusion into Fe overlayer and weaken the interaction of As and Fe. It results in enhancing the magnetism of Fe overlayer on GaAs(100). We also investigate the effects of the pre-annealing of S- passivated GaAs(100) substrate on the magnetism of Fe overlayers. The results show that the maximum effective magnetization can be obtained at annealing temperature of 400 °C. According to the experimental results of synchrotron radiation photoemission, it can be explained by the change of chemical composition and surface structure of the passivation layer on GaAs(100) surface after the annealing.

Study of iron overlayer on sulphur passivated GaAs(100) by synchrotron radiation photoemission

We have studied the interface electronic structures and the chemical reaction of the Fe overlayer deposited on S-passivated GaAs(100). The chemical bond and electronic structure are different from Fe/GaAs, and the reaction between As and Fe is weakened by S atoms. This is beneficial to the magnetism in the interface. In the first stage of deposition, Fe clusters is form near S atoms due to the large electronegativity of S. The S atoms remain at the interface with Fe coverage. Magnetic ordering feature is found at a coverage higher than 0.6 nm. According to the large exchange splitting in valence band spectra, we suggest that Fe phase transition from bcc to fcc occurs with increasing coverage.

Soft-x-ray photoemission study of Mn/GaP(100) interface

The interface formation and electronic structures of the Mn/GaP(100) interface are studied with synchrotron radiation photoemission. At the early stage of Mn deposition, Mn covers the whole GaP(100) surface. With the increase of coverage, Ga atoms can be exchanged by Mn atoms and diffuse into the Mn overlayer. However, P atoms remain always near the interfacial region. A significant difference of the electronic structures is observed between the ultra-thin and the thick Mn films. The explanations for this are given in the text.

Alkali Rb‐doped C60: The movement of the valence band (abstract)

Using synchrotron radiation light source, we have measured the photoemission spectra of undoped C60 and alkali Rb‐doped C60 to reveal their electron structure. We observed a complex movement of the top of the valence band through the process of alkali Rb doping. When Rb is doped into C60, at first the spectrum moves to the high binding energy side for about 0.5 eV. As doping continues, the spectrum moves to the low binding energy side again. The spectrum moves back toward the original site by a small amount until the stoichiometry reaches about 1. This phenomenon has not been reported in other alkali doped C60 systems. We suggest the backward movement is due to the instability of the RbC60, Rb3C60, and other phases.