Vickers diamond indentation at 370C was used to introduce dislocations into plate-like (00•¯1) N-polar single crystals. It was established that, when using a standard Vickers diamond indenter, well-defined rosettes of defects were formed under loads of 1.5 to 2N that were applied for 600s. Patterns of dislocation-related etch-pits were formed by using molten KOH-NaOH eutectic (200C, 90 to 120s). Individual grown-in dislocations were revealed by this etchant. Transmission electron microscopy confirmed the association of etch pits with individual dislocations that emerged at the surface. Nanocrystalline material was found in the highly deformed central region of the indentation rosette. The structure of the nano-crystals was analyzed by using electron diffraction techniques. It was speculated that a phase transition was induced by the high local pressures.

Study of Individual Grown-In and Indentation-Induced Dislocations in GaN by Defect-Selective Etching and Transmission Electron Microscopy. J.L.Weyher, M.Albrecht, T.Wosinski, G.Nowak, H.P.Strunk, S.Porowski: Materials Science and Engineering B, 2001, 80[1-3], 318-21