PHOTOEMISSION-STUDY ON THE SNO2/P A-SICX-H INTERFACE

Ultraviolet and X-ray photoemission spectroscopies (UPS and XPS) have been employed to SnO2 and its interface with P-type a-SiCx:H. The HeI valence band spectra of SnO2 show that the valence band maximum (VBM) shifts from 4.7 eV to 3.6 eV below the Fermi level (E(F)), and the valence band tail (VBT) extends up to the E(F), as a consequence of H-plasma treatments. The work function difference between SnO2 and P a-SiCx:H is found to decrease from 0.98 eV to 0.15 eV, owing to the increase of the work function of the treated SnO2. The reduction of SnO2 to metallic Sn is also observed by XPS profiling, and it is found that this leads to a wider interfacial region between the treated SnO2 and the successive growth of P a-SiCx:H.

PHOTOEMISSION-STUDY OF THE INTERFACIAL FORMATION PROCESS AND REACTIONS BETWEEN AL AND HYDROGENATED AMORPHOUS SI

Using photoemission spectroscopy and Auger electron spectroscopy, the interfacial formation process and the reactions between Al and hydrogenated amorphous Si are probed, and annealing behaviors of the Al/a-Si:H system are investigated as well. It is found that a three-dimensional growth of Al metal clusters which includes reacted Al and non-reacted metal Al occurs at the initial Al deposition time, reacted Al and Si alloyed layers exist in the Al/a-Si:H interface, and non-reacted Al makes layer-by-layer growth forming a metal Al layer on the sample surface. The interfacial reactions and element interdiffusion of Al/a-Si:H are promoted under the vacuum annealing.

Electron diffraction and photoemission studies of clean and water-covered Si(5,5,12) and Si(112) surfaces

The structure of silicon surfaces in the orientation range (113)-(5,5,12)-(337)-(112) has been investigated using high resolution LEED and photoemission both on a spherical and on flat samples. We find that Si(5,5,12) [5.3 degrees from (113) and 0.7 degrees from (937)] is the only stable orientation between (113) and (111) and confirm the result of Baski et al. [Science 269, 1556 (1995)] that it has a 2 x 1 superstructure with a very large unit cell of 7.68 x 53.5 Angstrom(2). Adsorption measurements of water on Si(5,5,12) yield a mobile precursor kinetics with two kinds of regions saturating at 0.25 and 0.15 ML which are related to adsorption on different sites. Using these results, a modified structure model is proposed. Surfaces between (113) and (5,5,12) separate into facets of these two orientations; between (5,5,12) and (112), they separate into (5,5,12) and (111) facets. (337) facets in this range may be considered as defective (5,5,12) facets.

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

The effect of a potassium overlayer on nitridation and oxidation of the InP(100) surface is investigated by core-level and valence-band photoemission spectroscopy using synchrotron radiation. In comparison with the K-promoted nitridation of the InP(110) surface obtained by cleavage in situ, we found that the promotive effect for the InP(100) surface cleaned by ions bombardment is much stronger and that the nitridation products consist of two kinds of complexes: InPNx and InPNx+y. The results confirmed that surface defects play an important part in the promotive effect. Furthermore, in contrast with K-promoted oxidation of InP(100) where bonding is observed between indium and oxygen, indium atoms did not react directly with nitrogen atoms during the K-promoted nitridation of InP(100). (C) 1995 American Vacuum Society.

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).

忆N.F.Mott教授

读了《物理》杂志34卷第9期吴自勤和阎守胜两位同志写的关于N.F.Mott教授的纪念文章,很有感触,这使我回忆起Mott教授的一些往事.从这些往事中我深受教育,所以多年来未能忘怀。

Photoemission evidence for dilute k-doped phase KxC（60） with x<0.2

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The growth of ZnO on bcc-In2O3 buffer layers and the valence band offset determined by X-ray photoemission spectroscopy

This work was supported by the 863 High Technology R&D Program of China (Grant Nos. 2007AA03Z402 and 2007AA03Z451), the Special Funds for Major State Basic Research Project (973 program) of China (Grant No. 2006CB604907), and the National Science Foundation of China (Grant Nos. 60506002 and 60776015). The authors express their appreciation to Dr. Tieying Yang and Prof. Huanhua Wang (Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences) for XRD measurements and helpful discussions.

Studies of timing for a TOF counter at external target facility

Timing and amplitude properties of a prototype scintillator TOF counter at an external target facility are studied with a cosmic rays test. The dependence of signal pulse height and time resolution on the coordinate along the scintillator TOF counter is investigated with two different discriminators. A time resolution of 165 ps can be achieved at the center of the counter with a constant fraction discriminator. Time resolution better than 150 ps is obtained at the center with a leading edge discriminator af...