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Influence of defect characteristics on the nanoindentation response of a ‐plane GaN thin films
Author(s) -
Kavouras P.,
Lotsari A.,
Kehagias Th.,
Georgakilas A.,
Komninou Ph.,
Dimitrakopoulos G. P.
Publication year - 2013
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201200542
Subject(s) - nanoindentation , materials science , sapphire , dislocation , transmission electron microscopy , thin film , composite material , molecular beam epitaxy , classification of discontinuities , slip (aerodynamics) , basal plane , modulus , discontinuity (linguistics) , crystallography , epitaxy , optics , nanotechnology , chemistry , layer (electronics) , laser , mathematical analysis , physics , mathematics , thermodynamics
a ‐plane ( $11{\bar {2}}0$ ) GaN thin films grown under various conditions on r ‐plane sapphire by plasma‐assisted molecular beam epitaxy (PAMBE) were characterized by nanoindentation and transmission electron microscopy (TEM) techniques. It was found that the increase of the built‐in threading dislocation (TD) density induces an increase on the values of both the nanohardness ( H ) and the reduced elastic modulus ( E* ). Characteristic single ‘pop‐in’ discontinuities were detected on the loading segments of the load–unload cycle. The TDs appear to cause a decrease of the load for the onset of the pop‐in discontinuity. The dependence of the elastoplastic behaviour on the TD density is attributed to their sessile character, causing them to become obstacles for basal plane slip.