Published online by Cambridge University Press: 15 February 2011
Studies of defects generated by high energy (>1 GeV) heavy ion irradiation in high-Tc superconductors have been performed by transmission electron microscopy (TEM). Our study shows that high dose irradiation leads to the formation of nano-twins, by which the columnar defects are connected. An analysis of the local Fourier components of the image intensity in [001] lattice images indicates that these new "twin" boundaries are much more diffuse than preexisting twin boundaries in YBCO. The mechanism of the formation of nano-twin boundaries on {110} planes and their possible relation to superconducting properties are discussed.