Superconducting W-C nanopillars fabricated by Ga+ focused ion beam induced deposition

Ga+ Focused Ion Beam Induced Deposition (FIBID) is a highly flexible, single-step nanopatterning technique that makes use of a focused beam of Ga+ ions to locally induce the decomposition of a gaseous precursor material. In combination with the W(CO)6 precursor, Ga+ FIBID is known to yield a W–C compound that is superconducting below 4.7 ​K. While most reports on Ga+ FIBID-grown W–C focus on in-plane patterning, we demonstrate here that growth along the vertical direction may also be achieved by successively stacking a series of individual patterns that get deposited on top of each other. The nanopillars obtained following this procedure reach up to 10 ​μm in height, and have an aspect ratio of around 50. They exhibit a 68% of metallic W in terms of atomic content, higher than the 40% detected in their in-plane counterparts, while maintaining the superconducting properties. This approach also opens up the possibility of tuning their height and growth angle with respect to the substrate, exhibiting potential applicability in the design of 3D superconducting devices.