Study on the morphology of dislocation-related etch pits on pyramidal faces of KDP crystals

Abstract

The generation of etch pits with clear morphology is an important prerequisite to study dislocation structures. A mixture of water and ethanol is used to etch pyramidal faces of rapidly grown KDP crystals. Vivid etch pits on {101} faces were created by the process of etching and polishing and investigated using an optical microscope and 3D confocal microscope. The formation mechanism of dislocation-related etch pits was speculated. There exists approximately a central symmetry relation between the morphology of the dislocation-related etch pits and dislocation hillocks on the same face. The arrangement order of the inclined sectors (I′ → II′ → III′) of the dislocation-related etch pits is in accordance with that of the vicinal sectors (I → II → III) of the dislocation hillocks. The inclined sectors are composed of steps with the same orientations, [ 1], [ 1 1] and [0 1 0], as the vicinal sectors on the (1 0 1) face. Due to crystal symmetry, the morphology of the dislocation-related etch pits on adjacent pyramidal faces possesses mirror symmetry. There is a central symmetry relation between the dislocation-related etch pits on the upper face and the bottom side of the same sample.