共查询到20条相似文献,搜索用时 0 毫秒
1.
R. Feder 《Solid State Communications》1977,21(12):1091-1094
A theory of angle-resolved spin-polarized photoemission is applied to a localized adatom-level on W(001). For unpolarized light, substantial spin-polarization effects are found, which depend sensitively on the position of the adatom relative to the substrate. The intensities produced by left- and righthand circularly polarized light exhibit a sizeable asymmetry. 相似文献
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G.L. Bona F. Meier M. Taborelli E. Bucher P.H. Schmidt 《Solid State Communications》1985,56(4):391-394
Spin polarized photoemission experiments are reported on NiMnSb which has been predicted to be a halfmetallic ferromagnet. The 100% polarization near photothreshold has not been observed. If an energy gap in the minority electron density-of-states should exist, it will be smaller than 0.5 eV. 相似文献
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H.C. Siegmann 《Physics Reports》1975,17(2):37-76
Information on electron polarization in magnetic materials has been obtained from optical absorption measurements, from photoemission studies and from tunneling and field emission experiments. The results obtained with different techniques are reviewed. Special emphasis is given to the analysis of the contradictory data obtained from ferromagnetic metals. Magnetic insulators and semiconductors tend to give results that can be interpreted within the framework of current interpretation schemes, but the results from metals call for new models of magnetism and electron emission. 相似文献
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The equation is formulated and accurately solved for the problem of the transport of photoexcited electrons which undergo scattering before reaching vacuum, with the formation of an electron-hole pair, as well as multiple scattering of elastic type. The analytical expressions obtained permit calculations of the spectral composition of the emitted-electron flux and the quantum yield of photoemission. The limiting expression for the probability that secondary electrons will reach the vacuum which is obtained when the elastic-scattering mechanism is switched off is compared with literature data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 86–92, October, 1987. 相似文献
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S. F. Alvarado F. Ciccacci S. Valeri M. Campagna R. Feder H. Pleyer 《Zeitschrift für Physik B Condensed Matter》1981,44(4):259-264
We have made a comparative study of the performance of spin polarized photocathodes based on molecular beam epitaxy (MBE) grown GaAs with Be-doping and on liquid phase epitaxy (LPE) grown GaAs with Zn-doping. The experiments were performed on GaAs (100), (110), and (111) surfaces atT-300 K. The photoelectron spin polarization (P) of the MBE-photocathodes is face dependent reaching 49% for the (111) surface, a value close to P=50% predicted by theory. In contrast for the LPE-photocathodes P is significantly lower (19P36%). Possible causes for the higher polarization of the MBE-photocathodes are investigated. The influence of the Zn- and Be-dopant is elucidated by theoretical model calculations which shows that replacing the Zn-dopant by Be reduces significantly the depolarization at very low temperatures, but not at room temperature. It is therefore concluded that theinterface region between the GaAs substrate and the MBE-GaAs layer grown on top of it strongly influences the performance of the source.On leave from the Istituto di Fisica Universitá di Modena I-41100 Modena Italy. 相似文献
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The spin polarization of photoelectrons emitted form La doped EuO was measured as a function of light energy up to hv = 11 eV, together with the quantum yield. The spectrum of spin polarization can be understood in terms of the energy level diagram of bulk EuO. 相似文献
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It is known that a paramagnetic surface sheet persists far below the Curie temperature in the ferromagnetic semiconductors EuO and EuS. We show that the observed spin-polarization of the photo- and field-emitted electrons is largely determined by spin-exchange collisions in the surface sheet. A single paramagnetic atomic layer may have a depolarizing effect of up to 50 per cent. Other circumstances in which the proposed model might apply are suggested. 相似文献
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C. Carbone T. Kachel R. Rochow W. Gudat 《Zeitschrift für Physik B Condensed Matter》1990,79(3):325-326
The origin of the core level splitting in the Fe 3s spectra has been investigated by spin resolved photoemission. The two Fe 3s spectral features, separated by 4.4 eV, are found to be characterized by large and opposite spin polarization. This observation proves that the exchange interaction is the main cause of the Fe 3s splitting. 相似文献
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I. A. Zeltser E. N. Moos O. V. Savushkin 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2017,11(1):138-141
The possibilities of interpreting the secondary-electron energy spectra and recording the X-ray photoemission of single-crystal silicon samples are examined. Detected shifts in the energy-spectrum extremum, as well as its height, and the entire energy-distribution form for different types of implanted and annealed Si samples, indicate the degree of ordering of surface atoms. The possibilities of employing the Friedel- oscillation model are discussed. 相似文献
11.
《Physics letters. A》1986,118(5):260-263
We report measurements of circularly polarized recombination radiation from a GaAs0.6P0.4 crystal bombarded with longitudinally spin polarized electrons of 10 eV energy. Qualitatively, this process can be considered as the inverse of the photoemission utilized in GaAs and GaAsP polarized-electron sources. The measured degree of circular polarization is 0.29%±0.06% if the crystal is cooled with liquid nitrogen and the incident electrons are 15%±3% polarized. 相似文献
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S. F. Alvarado 《Zeitschrift für Physik B Condensed Matter》1979,33(1):51-60
Spin polarized photoemission is used as a method to study the magnetic peoperties of solid surfaces. Here we consider those systems where the spin polarization is believed to be conserved during the photoemission process. The surface sensitivity of the experiment will be therefore mainly determined by the relative magnitudes of the escape depth of the photoelectrons and of the magnetic coherence length. We analyze both the temperature and magnetic-field dependence of the degree of spin polarizationP of the electrons emitted from single crystals of magnetite, Fe3O4, and thin films (D=2–3000 Å) of Fe, Co and Ni. These data yield information on 1) the temperature dependence of the magnetization of the surface, 2) the relative sizes of and, 3) changes of the magnetic moment of atoms in the surface layers, and 4) the surface magnetic anisotropy. We show that this technique emerges as a novel tool to study magnetic systems with free surfaces and to test the predictions of recent calculations of the magnetic properties of surfaces. Emphasis is given to the fact that only relative changes ofP and not its absolute values are relevant for an analysis of the data. 相似文献
13.
《Solid State Communications》1986,58(11):775-779
Spin polarized photoelectrons emitted from a NEA GaAs(100)-photocathode, which is activated in a special way with oxygen and cesium, can have a broad energy distribution with a maximum energy higher than expected for an one-photon excitation process within the bulk from the valence band edge into the conduction band. Also the shape of the energy distribution curves of the emitted electrons depends on the intensity of the incident light. This double-step excitation process is observed for aged and/or oxidized activation layers, especially for surfaces with a strongly developed, negative electron affinity. To give an explanation of these effects, it is suggested that excited conduction electrons absorb a further photon within the band bending region. This second photoemission excitation step seems to be enhanced by an interfacial barrier between the band bending region and the cesium-oxygen activation layer as well as by the existence of two-dimensional surface subbands. 相似文献
14.
We report on the first energy-resolved (retarding field mode) spin polarized photoemission measurement from a Ni(111) single crystal using synchrotron radiation from the ACO storage ring at LURE(ORSAY) It is shown that exchange effects can be detected for electron states well below the Fermi energy and that spin polarized, constant-initial-state spectroscopy of ferromagnets using synchrotron radiation is feasible. 相似文献
15.
C. J. Powell 《Solid State Communications》1972,10(12):1161-1164
Measurements are reported of Al valence-electron excitation by Ka1,2 X-rays internally generated in evaporated specimens by electron bombardment. The X-ray photoelectron energy distribution is consistent with the u.v. distribution of Huen and Wooten. Weak structures are found in the energy distribution at positions corresponding to those in the calculated density of states. 相似文献
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Salamin YI 《Optics letters》2007,32(1):90-92
Fields of a radially polarized laser beam developed recently [Y. I. Salamin, Opt. Lett.31, 2619 (2006)] are employed to show that electrons produced by atomic ionization near the focus may be accelerated to GeV energies. Conditions for producing a mono-energetic and well-collimated electron beam are discussed. 相似文献