Vertical Growth of Superconducting Crystalline Hollow Nanowires by He<sup>+</sup> Focused Ion Beam Induced Deposition.

Córdoba, Rosa; Ibarra, Alfonso; Mailly, Dominique; De Teresa, José Ma · Nano Lett · 2018

basic_science · Level V

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Abstract

Novel physical properties appear when the size of a superconductor is reduced to the nanoscale, in the range of its superconducting coherence length (ξ<sub>0</sub>). Such nanosuperconductors are being investigated for potential applications in nanoelectronics and quantum computing. The design of three-dimensional nanosuperconductors allows one to conceive novel schemes for such applications. Here, we report for the first time the use of a He<sup>+</sup> focused-ion-beam-microscope in combination with the W(CO)<sub>6</sub> precursor to grow three-dimensional superconducting hollow nanowires as small as 32 nm in diameter and with an aspect ratio (length/diameter) of as much as 200. Such extreme resolution is achieved by using a small He<sup>+</sup> beam spot of 1 nm for the growth of the nanowires. As shown by transmission electron microscopy, they display grains of large size fitting with face-centered cubic WC<sub>1-x</sub> phase. The nanowires, which are grown vertically to the substrate, are felled on the substrate by means of a nanomanipulator for their electrical characterization. They become superconducting at 6.4 K and show large critical magnetic field and critical current density resulting from their quasi-one-dimensional superconducting character. These results pave the way for future nanoelectronic devices based on three-dimensional nanosuperconductors.