Stair-step columnar defects in ion-irradiated Bi2Sr2CaCu2Ox crystals

Bi2Sr2CaCu2Ox single crystals irradiated by 75 MeV B and 230-MeV Au ions we re investigated using transmission electron microscopy. Apart from columnar and cascade defects, another type of defect with stair-step morphology was observed in all the samples irradiated under the two different irradiation conditions. Such defects usually exist in the area, where the density of t he ion energy deposited is lower than that required for producing cascade d efects. The analyses of the defect microstructure and the location of the d efect in the target material indicate that this kind of defects is neither simple cracks nor ordinary irradiation-induced defects. The mechanism for t he formation of this kind of stair-step defect is qualitatively discussed. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.