Screw dislocations of YBa 2Cu 3O 7−γ single crystal revealed by chemical etching

Abstract

Crystallographic defects in (001), (100)/(010) and (011) faces of YBa 2Cu 3O 7−γ (YBCO) single crystals are revealed by chemical etching. There is clear evidence for spiral hillocks and growth steps. Screw dislocation etch pits are observed to be square pyramids with growth steps along the 〈100〉 / 〈010〉 and truncated by the 〈110〉 edges. The etching rate is anisotropic with V a〈100〉 > V a〈100〉/〈010〉 > V c〈001〉 > V i〈111〉. The density of the dislocation etch pits is of the order of 10 5 cm -2 on the (001) and 10 4 cm -2 on the (100)/(010) surfaces.