Artificial vortex pinning arrays in superconducting films deposited on highly ordered anodic alumina templates

Abstract

A simple procedure is described for creating periodic vortex pinning centers in thin superconducting NbN films. We report on three different strategies which involve the use of highly ordered alumina templates. In this approach, NbN thin films are deposited either on the porous face of the template made of a triangular array of nanoholes or on the triangular array of bumps formed by the barrier layer or even on the top of perpendicularly oriented ferromagnetic nanowire arrays obtained by electrochemical deposition, thus forming superconductor-ferromagnet hybrids. In all cases, the ordered template allows NbN films to form a periodic pinning array during its growth. The interpore (or inter-bump) distance ranged between 50 and 100 nm and adjustable pore (or wire) diameter was varied between 30 and 60 nm. Numerous matching effects have been observed up to 2.5 T and are maintained at low temperature. These fields are considerably higher than those typical for periodic pinning arrays made by lithographic techniques, which reflects the benefits of nanostructuring superconductors by using self-organized growth to enhance vortex pinning in a large field and temperature range.

Superconducting Quantum Metamaterials from Convergence of Soft and Hard Condensed Matter Science

“…For example, the introduction of simple 1D or 2D ordered porosity can create arrays of artificial flux pinning centers and enhance the critical field, among other properties. [ 8,9 ] The expansion of optical metamaterials paradigms to superconducting, 3D ordered phases is further expected to offer unique low‐loss and switchable metamaterials. [ 10,11 ] However, the exploration of these phenomena is extremely limited by a lack of synthetic strategies to prepare 3D ordered mesostructured superconducting materials.…”

Fabrication of Superconducting Nanowires Using the Template Method

“…Therefore, this second approach has also attracted researchers to these effects. Of course, such experiments were carried out using conventional metallic type-II superconductors, such as Nb, NbN, or MoGe [ 46 , 47 , 48 , 49 , 50 , 51 ], as AAO is not a reasonable template for HTSc thin films. These experiments will be discussed in Section 3.4 below.…”

“…In Refs. [ 46 , 47 , 48 , 49 , 50 , 51 ] large scale superconducting antidot arrays were grown from Si-supported anodized alumina substrates. Figure 10 a presents an SEM micrograph of a Nb film on top of an AAO template, and (b) gives a schematic representation showing the deposition of a 10 nm thick Al O insulating layer and of a 25 nm thick NbN film on the extremities of an array of Ni nanowires embedded in a nanoporous alumina template.…”

Strong anisotropic transport of vortices in superconductors

“…Advances in lithography techniques allow the fabrication of pinning centers with desired shapes, sizes, and geometries . Besides finding ways to efficiently pin the vortices, the control and manipulation of the moving vortex system is another issue that is gaining increased attention .…”