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Dislocations Produced by Indentation Deformation of HPVE GaN Films
Published online by Cambridge University Press: 15 March 2011
Abstract
Vickers hardness tests on {0001} and (1120) faces of a relatively thick GaN film grown on a (0001) sapphire substrate have been performed in the temperature range 25-1200°C. The microstructure of the plastic zone around the indentation sites has been investigated by transmission electron microscopy (TEM). At room temperature, the hardness was measured to be 12.3 GPa on the basal plane, and 11.1 GPa on the prism plane. The hardness decreases gradually with increasing temperature up to ∼800°C and then shows a plateau between ∼800 and ∼1050°C after which it decreases again above ∼1100°C. In contrast to the rather straight dislocations produced by room-temperature indentation of the (0001) face, the dislocations generated by indenting the (1120) face at room temperature were curved and in the shape of half-loops emanating from the indentation sites on the prism planes. Such dislocations were not dissociated within the resolution of weak-beam TEM.
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