Gate‐Induced Critical Current Modulation in W–C Nanowires: The Role of Fabrication

ABSTRACT

Gate‐voltage control of the superconducting critical current ( I _c ) is expected to play a central role in superconducting electronics and quantum circuits, yet the underlying modulation mechanism remains unclear and reported V _g values vary widely with the fabrication process. Using superconducting W–C nanowires grown by focused ion beam induced deposition (FIBID), we investigate how fabrication affects I _c modulation. A three‐step focused ion beam (FIB)‐based process—(1) electron beam lithography with lift‐off, (2) He ⁺ or Ga ⁺ FIBID nanowire growth, and (3) Ga ⁺ FIB etching for cleaning—was compared with a reference process lacking the final step. We measured transport and inter‐gate leakage in devices with varied gate and nanowire widths and different ion species. Three‐step devices required larger V _{g, offset} than the reference device, while the analysis in terms of a nominal inter‐gate electric‐field scale and dissipated gate power indicates that fabrication‐dependent leakage pathways govern the apparent voltage scale. The observed µW‐level dissipation is consistent with leakage‐induced, phonon‐mediated suppression of superconductivity, while V _{g, offset} variations reflect fabrication residues and FIBID‐induced substrate damage. These results show that I _c suppression in W–C nanowires is fabrication‐dependent and highlight controlled FIB processing combined with systematic transport measurements as an effective route to disentangle competing mechanisms in superconducting device design.