YBCO and NdBco nanowires grown by the alumina template method

High-Tc superconducting YBa₂Cu₃Ox (YBCO) and NdBa₂Cu₃Ox (NdBCO)nanowires are grown by the anodized alumina template method, starting from presintered123 powder. As templates, we have employed commercially available aluminatemplates with pore diameters of 100 nm and 20 nm, respectively, and an overallthickness of 50 μm. An additional oxygen annealing step is required to obtainsuperconducting nanowires. Superconductivity with a transition temperature of 88 K(YBCO) and 96 K (NdBCO) is confirmed by means of magnetic susceptibilitymeasurements (SQUID, AC susceptibility). The resulting nanowires are analyzed indetail employing electron microscopy (SEM, TEM) and atomic force microscopy (AFM).The separation of the nanowires of the templates is not yet established, but individualnanowires of up to 10 μm length could be separated from the template. In several cases,the template pores are not completely filled by the superconducting material, whichimplies that the observed length of approx. 10 μm is similar to what could be expectedfrom regular grain growth. Furthermore, resistance measurements using cut pieces of thefilled templates were carried out as a function of temperature. These pieces were coveredwith Au films on top and bottom in order to provide the electric contacts. Themeasurements confirmed the magnetically determined critical temperatures.