Search Results - (Author, Cooperation:M. Chafai)
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1Latest Papers from Table of Contents or Articles in PressM. Willem ; S. Tahirovic ; M. A. Busche ; S. V. Ovsepian ; M. Chafai ; S. Kootar ; D. Hornburg ; L. D. Evans ; S. Moore ; A. Daria ; H. Hampel ; V. Muller ; C. Giudici ; B. Nuscher ; A. Wenninger-Weinzierl ; E. Kremmer ; M. T. Heneka ; D. R. Thal ; V. Giedraitis ; L. Lannfelt ; U. Muller ; F. J. Livesey ; F. Meissner ; J. Herms ; A. Konnerth ; H. Marie ; C. Haass
Nature Publishing Group (NPG)
Published 2015Staff ViewPublication Date: 2015-09-01Publisher: Nature Publishing Group (NPG)Print ISSN: 0028-0836Electronic ISSN: 1476-4687Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsPublished by: -
2Articles: DFG German National LicensesAlvarez, A. ; Jiménez, J. ; Chafai, M. ; Bonnafé, J. ; González, M. A.
[S.l.] : American Institute of Physics (AIP)
Published 1993Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: The reverse transition from the EL2 metastable state to the ground state is achieved by thermal annealing above 140 K. An optical recovery of the ground state photoresponse (1–1.3 eV) can be also done exciting with near band-gap light. We present herein a photocurrent study of the photoquenching transients starting from either a thermal recovery situation or an optically recovery one. It is seen that the recovered states are not the same for both of them. While the thermal recovery restores the ground state of EL2, the optical recovery restores another state, labeled EL2r, which gives a different photoquenching transient as compared to the ground EL2 level.Type of Medium: Electronic ResourceURL: -
3Articles: DFG German National LicensesStaff View
ISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: The transport properties, particularly free carrier density and mobility, of SiC are usually determined by the Hall effect. Raman spectroscopy has been shown to yield transport parameters similar to the Hall effect. The analysis of the longitudinal optical plasmon coupled (LOPC) modes in doped SiC provides such information. In the case of damped plasmons in n-type 4H–SiC, changes in the carrier concentration result in a frequency shift of the LOPC mode, which appears close to the A1(LO) phonon mode. The validity of this approach for different free carrier concentrations (plasma frequencies) and mobilities (plasmon damping constants) is analyzed. The theoretical results obtained show that reliable estimation of the free carrier density can be obtained from the frequency shift of the LOPC mode for low carrier concentrations. At such a carrier concentration a reliable correlation between the Raman shift of the LOPC mode and the plasma frequency is established, without noticeable influence of the plasmon damping constant. However, when the free electron concentration increases, a non-negligible influence of the plasmon damping constant on the Raman frequency shift of the LPOC mode is observed. Therefore reliable transport data can only be obtained by a full line-shape analysis. These results are confirmed by the experimental results obtained on n-type 4H–SiC bulk samples with free electron concentration between 1×1017 and 5×1018 cm−3. © 2001 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
4Articles: DFG German National LicensesChafai, M. ; Jiménez, J. ; Alvárez, A. ; Bonnafé, J.
Woodbury, NY : American Institute of Physics (AIP)
Published 1992Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: The optically induced EL2*-EL2 transformation is studied by photocurrent measurements, allowing the monitorization of the free-carrier generation during the near-band-gap (NBG) recovery excitation. The efficiency recovery spectrum is found to be anticorrelated with the NBG photocurrent spectrum. This observation rules out the possibility of a free-carrier assisted process as the main mechanism accounting for the NBG induced EL2*-EL2 reverse transformation.Type of Medium: Electronic ResourceURL: