Vickers indentation on the {001} faces of ZnS sphalerite under UV illumination and in darkness. Crack patterns and rosette microstructure

Vickers microhardness indentations are performed on the (001) surface of ZnS sphalerite single crystals in darkness and under UV illumination, close to the band absorption edge. For low applied loads, the crack length and the rosette size confirm the hardening effect of illumination (positive photoplastic effect) that causes a lowering of the dislocation mobility. For high applied loads the positive photoplastic effect is masked by a strong workhardening in the highly strained zone. In darkness as well as under irradiation, perpendicular rosette arms have the same length, showing that alpha and beta perfect dislocations have similar mobilities at variance with III-V compounds. However, the observed asymmetry in the dissociation behaviour suggests that partial dislocations have different mobilities. Copyright (C) 1996 Acta Metallurgica Inc.