Spiral etch pits in KBr single crystals

Abstract

Freshly cleaved (100) cleavages of KBr single crystals grown in the laboratory have been etched in an etchant containing 10 ml absolute ethyl alcohol, 0·5 ml n-butyl alcohol, 0·1 ml formaldehyde and 0·1 ml distilled water. Both clockwise and anticlockwise spiral etch pits are produced. By etching (100) matched cleavage pairs in the same conditions, one-to-one correspondence in number, position and shape but not the sense of some of the spirals has been established. By re-etching a cleavage face having spiral etch pits in dislocation etchant, an etch pit is formed exactly at the centre of each spiral, indicating thereby that the spiral etch pits nucleate at the sites of dislocations terminating on the crystal face. The implications are discussed.