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Long columnar nano-defects were formed in a Bi 2 Sr 2 CaCu 2 O x (Bi2212) single crystal irradiated by 230 MeV Au and 180 MeV Fe ions. As expected, the width of the columnar defects induced by the heavy Au ion irradiation gradually decreased with the loss of ion energy in the target along the ion trace. However, in the case of irradiation by the lighter Fe ions, the width of the columnar defects remained almost constant along the ion trace. The conditions required for producing the same type of damage morphology in the same target are very different for the two types of ions, strongly depending on the ion momentum, and hence mass. The relationships between the ion energy and the columnar defect size produced by the two types of irradiation are discussed quantitatively. The relationships are found to be useful for predicting the diameters and distribution of the columnar defects formed by ion irradiation.

Bi2Sr2CaCu2Ox single crystals were irradiated with 18MeV Fe8+ ion at room temperature. Superconductive property and microstructure of the samples after the irradiation were investigated by magnetization hysteresis (ΔM) and transmission electron microscopy (TEM). ΔM was enhanced by increasing ion dose up to 1×1012ions/cm2, but decreased at the density of 1×1013ions/cm2. The ion irradiation produced ellipse-like amorphous defects with the size of several nm, which may behave as flux pinning centers inside the crystals. The defects were formed in the band region of 0.5μm at the depth of about 4.5μm from the surface. The number of defects were equal to several times of applied ion dose. The optimum dose for improving superconductivity should be dominated by the defect size and spacing of defects to avoid overlapping among the defects.