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Vacancy Clusters (vacancy + cluster)

Distribution by Scientific Domains

Physics and Astronomy	80%

Selected Abstracts

Ultra-Fast Atomic Transport in Severely Deformed Materials,A Pathway to Applications?,

ADVANCED ENGINEERING MATERIALS, Issue 8 2010
Sergiy Divinski
Abstract Severe plastic deformation of pure Cu and Cu-rich alloys was found to create a hierarchical combination of fast and ultra-fast diffusion paths ranging from non-equilibrium grain boundaries to non-equilibrium triple junctions, vacancy clusters, nano- and micro-pores, and finally to general high-angle grain boundaries. Under certain conditions, a percolating network of porosity can be introduced in the ultra-fine grained materials by a proper mechanical and thermal treatment. This network may offer promising opportunities for creating materials with tailor-made properties, including combinations of improved mechanical performance with a possibility of self repair using "vascular structures" for atom transport. Applications in such areas as drug eluting bioimplants and lead or polymer eluting materials for reduction of friction based on impregnation of porosity networks with these agents are also envisaged. [source]

Atomic structure of pyramidal defects in GaN:Mg: Influence of annealing

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006
Z. Liliental-Weber
Abstract The atomic structure of the characteristic defects (Mg-rich hexagonal pyramids) in p-doped bulk and MOCVD GaN:Mg thin films grown with Ga polarity was determined at atomic resolution by direct reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities were present inside the defects, confirmed also with positron annihilation. The inside walls of the cavities were covered by GaN of reverse polarity compared to the matrix. Annealing of the MOCVD layers lead to slight increase of the defect size and an increase of the room temperature photoluminescence intensity. Positron annihilation confirms presence of vacancy clusters of different sizes triggered by the Mg doping in as-grown samples and decrease of their concentration upon annealing at 900 and 1000 °C. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

PALS investigation of chromium effect in ferritic/martensitic steels implanted with helium

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2009
Stanislav Sojak
Abstract Chromium is an element with significant effect on the elevated temperature corrosion resistance and the low radiation induced void swelling. There were several studies carried out with regard to effect of Cr on the defect creation and stability [1, 2], but this issue is not fully understood yet. This paper contributes to this research with the study of Fe-Cr binary alloys with different Cr content, implanted by helium by the use of cascade accelerator and investigated by conventional PALS set-up. Our measurements show that chromium plays a role in the formation of small vacancy clusters, affecting the size and distribution of these defects. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Decorated vacancy clusters in Si and thin C films grown on Si studied by depth profiling positron annihilation spectroscopies

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2007
R. S. Brusa
Abstract The combined use of different depth profiling positron annihilation spectroscopies give insight on distribution, type and decoration of open-volume defects. Applications regarding defects produced in modified silicon and at the interface between deposited thin films and the silicon substrate are presented. The attention is focused on selected systems and situations potentially related to technological developments: a) identification of decorated vacancy clusters in silicon implanted by light-ion (He, He+H) and evolution of the clusters with the thermal treatments; b) release of compressive stress through vacancy-like defects formation at the interface during the growth of thin (10-200 nm thick) carbon films. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]