Superconductivity in Tungsten-Carbide Nanowires Deposited from the Mixtures of W(CO)₆and C₁₄H₁₀

Abstract

Tungsten-carbide (W-C) nanowires have been deposited by focused-ion-beam chemical vapor deposition (FIB-CVD). Mixtures of C14H10 and W(CO)6 are used as precursors. For certain precursor ratios, our nanowires become superconducting with a T c as high as 5.8 K. Also, freestanding W-C nano pillars were grown by FIB-CVD. The growth rate of the deposition from the mixture is at most 4.25 times higher than W(CO)6 is used as the precursor. This growth rate greatly facilitates the fabrication of three-dimensional superconducting structures.

Elucidating the role of disorder introduced by nitrogen in the superconducting properties of tungsten thin films

“…When nitrogen impurities stabilize -phase, the films display T c up to 4.7 K 5 . The latter agrees with reports for amorphous structures obtained by focused ion beam (FIB) assisted deposition [13][14][15][16] , suggesting that the disorder at the nanoscale plays a role in the superconducting properties of W nanostructures. Indeed, nanowires with T c  4.8 K were obtained by FIB using tungsten hexacarbonyl and a gallium beam where the impurities are mainly C, Ga and O [13][14][15] .…”

Direct-Write Printing of Josephson Junctions in a Scanning Electron Microscope

“…Such high currents, however, can lead to electrostatic charging effects and larger beam spots, which limit our control over device fabrication. The bottom line here is that EBID can provide superconducting W–C with a T c that is comparable to those written by IBID using Ga + ions. − …”

“…Whereas the superconducting transition temperature ( T c ) of pure crystalline tungsten is only 0.011 K, disordered and amorphous tungsten alloys with Si, C, and Ge can have a T c around 6 K . The precursor W­(CO) 6 has been widely implemented for ion-beam-induced deposition (IBID), usually with a focused Ga + or He + beam, to fabricate superconducting structures. − Exposure to ion beams, however, is unavoidably accompanied by ion implantation and beam-induced disorder, which are detrimental to pristine systems ( e.g. , graphene).…”

Direct-write of tungsten-carbide nanoSQUIDs based on focused ion beam induced deposition

“…The superconducting properties of W-C fabricated by Ga + FIB irradiation of the commercially available precursor gas W(CO) 6 are well studied. 24 Planar Ga + FIBID W-C deposits exhibit a critical temperature of T c ¼ 4-5 K, [25][26][27][28] an upper critical magnetic eld of B c2 ¼ 7-8.5 T [29][30][31] and a critical current density of J c ¼ 0.01-0.1 MA cm −2 . [26][27][28] The London penetration depth is reported to be l L ¼ 850 nm 32,33 and the superconducting coherence length x ¼ 6-9 nm.…”