The mechanism of the recrystallization process in epitaxial GaN under dynamic stress field: atomistic origin of planar defect formation

Abstract

The mechanism of the recrystallization in epitaxial (0001) GaN film, introduced by the indentation technique, is probed by lattice dynamic studies using Raman spectroscopy. The recrystallized region is identified by micro‐Raman area mapping. ‘Pop‐in’ bursts in loading lines indicate nucleation of dislocations and climb of dislocations. These processes set in plastic motion of lattice atoms under stress field at the center of indentation for the initiation of the recrystallization process. A planar defect migration mechanism is evolved. A pivotal role of vacancy migration is noted, for the first time, as the rate‐limiting factor for the dislocation dynamics initiating the recrystallization process in GaN. Copyright © 2009 John Wiley & Sons, Ltd.

Direct observation of amophization in load rate dependent nanoindentation studies of crystalline Si

“…These high stresses are reported for pressure-induced phase transformations to denser crystalline ͑c-͒ and amorphous forms in monovalently 1 and covalently bonded compound 2 semiconductors along with plastic deformation, leading to recrystallization by annihilation of dislocation in ionic bonded compound semiconductors. 3,4 Phase transformation of Si under controlled pressure is of renewed interest in the age of ion cutting and ion doping to suit microelectromechanical and nanoelectromechanical systems ͑MEMS and NEMS͒ systems. 5 The study of transformation to the high pressure phase has technological importance for having control in the precision micromachining process steps using enhancement of ductility in these systems.…”

Raman Mapping for the Investigation of Nano-phased Materials

“…The stress can reach very high values locally (as evidenced through wavenumber shifts) and the Raman study of micro/nano-indentations is a possible way of monitoring phase transitions under non hydrostatic stress [140,141]. Mapping capabilities are a great asset as the pressure conditions vary from one point to another (the imprints dimensions are in the range of a few tens of micrometers) because of the imperfect geometry of the indenters, the possibility of intragranular versus intergranular indentation, crack propagation at the imprints corners, materials pileup at the imprint periphery, etc., [38,44,[141][142][143][144][145][146][147][148]. Figure 3.20 illustrates the Raman mapping of a Vickers microindentation in ZnSe.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part IV

“…The IR and Raman spectra of anhydrous lead oxalate (PbC 2 O 4 ) were recorded and discussed by Mancilla et al 214 on the basis of its structural peculiarities, and comparisons with other previously investigated metallic oxalates were made. Das et al 215 have studied the mechanism of the recrystallization in epitaxial GaN under a dynamic stress field and described the atomic origin of its planar defect formation. SiC is often used for electronic devices operating at elevated temperatures.…”