Indexed on: 23 Jan '18Published on: 23 Jan '18Published in: Nano Letters
Novel physical properties appear when the size of a superconductor is reduced to the nanoscale, in the range of its superconducting coherence length (ξ0). Such nano-superconductors are being investigated for potential applications in nano-electronics and quantum computing. The design of three-dimensional nano-superconductors allows one to conceive novel schemes for such applications. Here, we report for the first time the use of a He+ focused-ion-beam-microscope in combination with the W(CO)6 precursor to grow three-dimensional superconducting nanotubes as small as 32 nm in diameter and with an aspect ratio (diameter/length) of as much as 200. Such extreme resolution is achieved by using a small He+ beam spot of 1 nm for the growth of nanotubes. As shown by transmission electron microscopy, they display grains of large size fitting with face-centered cubic WC1-x phase. The nanotubes which are grown vertically to the substrate, are felled on the substrate by means of a nano-manipulator 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 nano-superconductors.