Purified and Crystalline Three-Dimensional Electron-Beam-Induced Deposits: The Successful Case of Cobalt for High-Performance Magnetic Nanowires

Focused-electron-beam-induced deposition (FEBID) is considered the ultimate direct-write lithography technique for three-dimensional (3D) structures. However, it has not yet been possible to obtain 3D deposits by FEBID with the same purity and crystallinity of the corresponding bulk materials. In the present work, purified and crystalline 3D Co nanowires of diameter below 90 nm have been fabricated by ex situ high-vacuum annealing at 600 °C after FEBID growth. With an increase of the metallic content of the nanowires up to 95 atom %, the thermal annealing process induces recrystallization of the pseudoamorphous as-grown structure into bulklike, hexagonal-closest-packed, and face-centered-cubic crystallites with lateral sizes comparable to the nanowire’s width. The net magnetization increases 80% with respect to the as-grown values, up to 1.61 ± 0.06 T, near bulk Co. This achievement opens new pathways for applications of this synthetic method in the fabrication of either individual or arrays of 3D high-purity and crystalline Co nanowires for high-density memory and logic devices, nanosensors, and actuators, and could be a viable method to obtain other pure and crystalline 3D materials by FEBID.