The barrier layer of self-ordered anodized aluminium oxide, which is grown from an aluminium foil, has been revealed by a selective chemical etching of the remaining aluminium. The surface obtained in this way consists of a triangular lattice of bumps with 100nm spacing, and heights of approximately 50nm. Using this surface as a template for controlling the pinning in thin superconducting films, superconducting Nb was deposited with different thicknesses and under different deposition angles. The evaporation under a 30° angle shows an asymmetric pinning potential composed of two triangular lattices having different pinning strengths. Matching effects are observed up to 1T. Matching effects are also maintained at relatively low temperature.
Hallet, X., Mátéfi-Tempfli, S., Mátéfi-Tempfli, M., Michotte, S., Piraux, L., Vanacken, J., & Moshchalkov, V. V. (2009). Artificial pinning centers using the barrier layer of ordered nanoporous alumina templates. Journal of Physics: Conference Series (Online), 153. https://doi.org/10.1088/1742-6596/153/1/012013