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Vacancy Defects (vacancy + defect)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Observation of interfacial electrostatic field-induced changes in the silicon dielectric function using spectroscopic ellipsometry

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008
J. Price
Abstract This work investigates the capability of spectroscopic ellipsometry to measure charge trapping centers in thin dielectric films. Specific interfacial electrostatic fields, induced by electrons injected into charge trapping states at the interface, have been identified that directly affect the underlying silicon substrate critical points. The effect of a field-induced change in the silicon fundamental absorption edge due to different processing conditions affecting the oxygen vacancy defects at the interface is presented. Measuring the field-induced change in the silicon dielectric function between a sample with a 2 nm HfO2 film as-deposited and the same sample after a 1000 °C anneal in an N2 ambient reveals that a stronger interfacial field is present for the as-deposited HfO2 film. These results are consistent with the understanding that high temperature anneals work well to passivate oxygen vacancy defects at the silicon/HfO2 interface. Finally, we compare our results with Second Harmonic Generation where specific resonant features are identifiable with electric field enhancements at the same interface. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Cathodoluminescence properties of zinc oxide nanoparticles

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2004
M. R. Phillips
Abstract Zinc oxide nano-particles (25 nm) have been investigated by cathodoluminescence spectroscopy (300 nm,1700 nm) at 80 K and 300 K following thermal annealing in high purity H2/N2, N2, O2 and Ar gaseous atmospheres. The intensity of the ZnO near band edge peak was significantly increased after heat treatment in hydrogen. Conversely, thermal annealing in the other gas types decreased this emission. This effect is attributed to hydrogen passivation of competitive non-radiative defect centers, most likely bulk zinc vacancy centers. The appearance of a strong green emission centered at 2.4 eV following thermal annealing in all gas atmospheres is ascribed to the formation of bulk oxygen vacancy defects. A strong red shift of the near band edge emission with increasing beam current at 300 K is accredited to electron beam heating rather than to an increase in the carrier density. Electron beam heating is evidenced by the occurrence of a strong black body emission in the near infrared spectral region. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Observation of Zn vacancies in ZnO grown by chemical vapor transport

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2006
F. Tuomisto
Abstract We have used positron annihilation spectroscopy to study the vacancy defects in ZnO crystals grown by both the conventional and contactless chemical vapor transport (CVT and CCVT). Our results show that Zn vacancies or Zn vacancy related defects are present in as-grown ZnO, irrespective of the growth method. Zn vacancies are observed in CVT-grown undoped ZnO and (Zn,Mn)O. The Zn vacancies present in undoped CCVT-ZnO are the dominant negatively charged point defect in the material. Doping the material with As introduces also Zn vacancy-related defect complexes with larger open volume. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Positron annihilation characteristics in UO2: for lattice and vacancy defects induced by electron irradiation

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2007
M.-F. Barthe
Abstract In this work both 22Na based positron lifetime spectroscopy (PALS) and slow positron beam based Doppler annihilation-ray broadening spectrometry (SPBDB) have been used to characterize respectively the bulk and the first micron under the surface of sintered UO2 disks that have been polished and annealed at high temperature (1700 °C/24 h/ArH2). Results show the presence of negative ions that are tentatively identified to negatively charged oxygen atoms located in interstitial sites. The positron annihilation characteristics in the UO2 lattice have been determined and are equal to SL(UO2) = 0.371(5), WL(UO2) = 0.078(7), ,L(UO2) = 169 ± 1 ps. Such disks have been irradiated at room temperature with electrons and , particles at different fluences. After irradiation SPBDB and PALS measurements show the formation of U-related vacancy defects after a 2.5 MeV electrons irradiation whereas no defects are detected for an irradiation at 1 MeV. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]