Search results for "Positron annihilation spectroscopy"
showing 2 items of 12 documents
Characterization of non-polar ZnO layers with positron annihilation spectroscopy
2008
We applied positron annihilation spectroscopy to study the effect of growth polarity on the vacancy defects in ZnO grown by metal-organic vapor phase deposition on sapphire. Both c-plane and a-plane ZnO layers were measured, and Zn vacancies were identified as the dominant defects detected by positrons. The results are qualitatively similar to those of earlier experiments in GaN. The Zn vacancy concentration decreases in c-plane ZnO by almost one order of magnitude (from high 10 cm−3 to low 10 cm−3) when the layer thickness is increased from 0.5 to 2 μm. Interestingly, in a-plane ZnO the Zn vacancy concentration is constant at a level of about 2×10 cm−3 in all the samples with thicknesses v…
Structural-relaxation phenomena in As–S glasses as probed by combined PAL/DBAR technique
2015
Abstract Experimental techniques exploring phenomena of positron–electron interaction, namely the positron annihilation lifetime spectroscopy and Doppler broadening of annihilation radiation, are shown to be very informative tools to study radiation- and thermally-induced phenomena in chalcogenide glasses of binary As–S system. Time-dependent processes of free-volume voids agglomeration (expansion), fragmentation (refining) and disappearing (contraction) are identified as main stages of physical aging in S-rich glasses, while a competitive channel of coordination topological defects formation associated with void charging becomes significant in a vicinity of near-stoichiometric glass compos…