Generation and Relaxation of Microstrains in GaN Nanocrystals under Extreme Pressures
E. Grzankaa,b, B. Palosza, S. Gierlotkaa, R. Pielaszeka,b, U. Bismayerc, J.F. Janikd, J.R. Wellse, W. Paloszf and F. Porschg
aHigh Pressure Research Center UNIPRESS, Soko³owska 29/37, 01-142 Warsaw, Poland
bInstitute of Experimental Physics, Warsaw University, Warsaw, Poland
c Mineral-Petrographisches Institut, University of Hamburg, Hamburg, Germany
dUniversity of Mining and Metallurgy, Cracow, Poland
eDepartment of Chemistry, Duke University, Durham, USA
fUSRA/NASA-Marshall Space Flight Center, Huntsville, Alabama, USA
gMineralogisch-Petrologisches Institut der Rheinischen Friedrich-Wilhelms-Universitäat Bonn, Bonn, Germany
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Nanocrystalline powders of GaN with grain sizes ranging from 2 to 30 nm were examined under high external pressures by in situ diffraction techniques in a diamond anvil cell at DESY (HASYLAB, Station F3). The experiments on densification of pure powders under high pressure were performed without a pressure medium. The mechanism of generation and relaxation of internal strains and their distribution in nanoparticles was deduced from the Bragg reflections recorded in situ under high pressures at room temperature. The microstrain was calculated from the full-width at half-maximum (FWHM) values of the Bragg lines. It was found that microstrains in GaN crystallites are generated and subsequently relaxed by two mechanisms: generation of stacking faults and change of the size and shape of the grains occurring under external stress.
DOI: 10.12693/APhysPolA.102.167
PACS numbers: 61.46.+w, 81.07.Wx