排序方式: 共有27条查询结果,搜索用时 67 毫秒
1.
2.
We present spin polarization and energy distribution curves of photo-electrons from US and compare them with a density of states calculation based on a cluster method. For photon energies hv ≤ 11 eV the photo-electron spin polarization is negative. Near threshold a structure is observed in the spectra, which is attributed to emission from the 5f-states. 相似文献
3.
Spin polarized LEED results are presented which confirm predicted symmetry induced properties. Contrary to recent claims, the results do not provide any evidence for a broken bulk derived symmetry in the Au(110) surface. 相似文献
4.
We present the first angle-, energy-, and spin-resolved measurements of secondary electrons emitted from a Au(110) surface bombarded with unpolarized electrons. Both transversal components normal to and in the scattering plane, of the spin polarization vector exist. A simple two-step scattering process explains the observations, where the polarization is created via spin-orbit coupling in collisions of secondary electrons with ion-cores. 相似文献
5.
Well-defined (101) and (001) surfaces of anatase TiO2 were studied for the first time by secondary-electron imaging and low-energy electron diffraction. Initially, both surfaces show a crystalline structure corresponding to the bulk anatase phase, buried under an atomically thin contamination layer. After mild sputtering with 500 eV Ne+ ions, we have observed a surface phase transition from tetragonal anatase to face-centered cubic titanium monoxide TiO. Subsequent annealing at 900 K restores the (1×1) anatase structure at the (101) surface. On the (001) surface, however, a (1×4) reconstruction appears. The unreconstructed structure can be recovered by exposing the surface to oxygen. These observations demonstrate the stability of the anatase surfaces and illustrate the feasibility of preparing and investigating clean surfaces of this technological important form of TiO2. 相似文献
6.
B. Bolliger M. Erbudak D. D. Vvedensky A. R. Kortan 《Czechoslovak Journal of Physics》1999,49(11):1531-1536
Twofold-, threefold-, and fivefold-symmetry elements are observed in the near-surface region of the quasicrystal Al70Pd20Mn10 using a real-space imaging technique based on secondary-electron emission. The observed icosahedral point-group symmetry
implies the presence of atomic clusters within the analyzed region of the solid. The same surface produces perfect low-energy
electron diffraction patterns typical for well-defined crystallographic planes. We present a model which reconciles this dual
structural nature of quasicrystals. Our model is constructed from an icosahedral seed followed by concentric symmetry-preserving
“growth” to form the macroscopic solid.
Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999.
This work was supported in part by the Schweizerischer Nationalfonds. 相似文献
7.
Oxygen-induced surface faceting of the threefold-symmetry surface of icosahedral AlPdMn quasicrystal
We have investigated the oxidation behavior of the threefold-symmetry surface of icosahedral AlPdMn quasicrystal by low-energy electron diffraction and Auger electron spectroscopy. Upon oxygen exposure at 740 K, the predominantly planar surface develops facets of an Al-oxide layer, each facet oriented along a high-symmetry direction of the icosahedral bulk structure. While the facets along the fivefold-symmetry directions are structurally well-ordered, the facets along the twofold- and threefold-symmetry directions are structureless. The results are compared with the oxide formation on the fivefold-symmetry surface of icosahedral AlPdMn quasicrystal. 相似文献
8.
9.
By means of congruent evaporation, we have deposited CdTe and PbTe onto the oxidized fivefold-symmetry surface of an icosahedral AlPdMn quasicrystal. This procedure results in the formation of nanocrystals in both cases. While the azimuthal orientations of the crystallites are random, the polar orientations are well defined. The crystalline CdTe and PbTe domains expose their (1 1 1) and (0 0 1) faces, respectively, which are aligned parallel to the pentagonal surface of the quasicrystal. The nanometric size of the domains is not a result of the lattice mismatch between the growing film and the substrate as usually observed in molecular-beam epitaxy, but of the limited size of the oxide domains of the substrate surface. 相似文献
10.
M. Erbudak V.A. Gubanov E.Z. Kurmaev 《Journal of Physics and Chemistry of Solids》1978,39(11):1157-1161
Experimental photoelectric- and X-ray emission spectra obtained from NbO are compared with the molecular orbital calculations of NbO610? cluster using Xα discrete variational method. The agreement between theory and experiment establishes the validity of the cluster approach to determine the electronic structure of the 4d transition metal chalcogenides. 相似文献