Nano-patterning of cuprate superconductors by masked He^+ ion irradiation: 3-dimensional profiles of the local critical temperature

Irradiation of cuprate high-$T_c$ superconductors with light ions of moderate energy creates point defects that lead to a reduction or full suppression of the critical temperature. By shaping the ion flux with a stencil mask, nanostructures for emerging superconducting electronics can be fabricated. The 3-dimensional shape of such defect landscapes is examined, based on calculations of full collision cascades and atom displacements. A relation between the calculated defect density and experimental values of the critical temperature $T_c$ in thin YBa$_2$Cu$_3$O$_{7-\delta}$ films is etablished that allows to determine the distribution of local $T_c$'s and its 3-dimensional visualization. The results confirm that, using 75 keV He$^+$ ion irradiation and a stencil mask, well-defined patterns of non-superconducting material in the superconducting matrix can be produced with low blurring.