X-ray topographic examination of loops and spiral dislocations in cadmium single crystals

Abstract

Abstract Dislocation loops and spirals were examined in nearly perfect cadmium single crystals by X-ray topography. Their Burgers vectors were precisely determined from dislocation contrast using six reflecting planes. Several types of dislocation configurations were identified: hexagonal or round simple loops; concentric multiple loops; complex loops; single and double pole spirals. The Burgers vector was found to be c = [0001] or c + a = ⅓ 〈11 3〉. The evolution of loops and spirals was observed in-situ during crystal heating or oxidation. The dislocations were seen to undergo large climbing movements. Their nucleation is interpreted in terms of the climb of c or c + a source-dislocations anchored at some points.