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

Abstract

Josephson junctions are the building blocks of superconducting electronics, with well-established applications in precision metrology and quantum computing. Fabricating a Josephson junction has been a resource-intensive and multistep procedure, involving lithography and wet-processing, which are not compatible with many applications. Here, we introduce a fully additive direct-write approach, where a scanning electron microscope can print substrate-conformal Josephson devices in a matter of minutes, requiring no additional processing. The junctions are made entirely by electron-beam-induced deposition (EBID) of tungsten carbide. We utilize EBID-tunable material properties to write, in one go, full proximity junctions with superconducting electrodes and metallic weak links and tailor their Josephson coupling. The Josephson behavior of these junctions is established and characterized by their microwave-induced Shapiro response and field-dependent transport. Our efforts provide a versatile and nondestructive alternative to conventional nanofabrication and can be expanded to print three-dimensional superconducting sensor arrays and quantum networks.

Critical current modulation induced by an electric field in superconducting tungsten-carbon nanowires

“…Paramountly, the material is type-II superconductor, with a critical temperature ( ) around 4.75 K, an upper critical magnetic field of 9.5 T, a critical current density of 0.01-0.10 MA/cm , and values for the coherence length and penetration depth of 6.25 nm and 850 nm, respectively 30 – 35 . Superconductivity has also been found to occur in the material yielded when the decomposition of W(CO) is induced by a focused electron beam instead, which has been exploited for the fabrication of Josephson junctions 36 . Remarkably, and contrary to most of the aforementioned superconducting materials, in which this phenomenon has been investigated, Ga FIBID W-C is not fully metallic, nor it is a highly crystalline, yet it allows for the occurrence of the effect, as it will be presented in the following sections.…”

Direct Writing of Cobalt Silicide Nanostructures Using Single-Source Precursors

“…A very important characteristic of the process is the maskless site-selective writing of nanostructures of the desired shape and dimension. A general introduction to the topic, including physics of the beam–substrate interactions, has been published, , while reviews focusing on precursors for FEBID are also available. , To date, the fields of application of FEBID-derived materials include predominantly fundamental research in nanoelectronics, , nanomagnetics, , plasmonics, , gas and force sensing, and superconductors. , …”

“…3,4 To date, the fields of application of FEBID-derived materials include predominantly fundamental research in nanoelectronics, 5,6 nanomagnetics, 7,8 plasmonics, 9,10 gas 11 and force sensing, 12 and superconductors. 13,14 The actual number of suitable FEBID precursors is still limited and additional information is required in order to fully understand and tailor on-demand specific precursors for this technique. 4 In this respect, either ligand systems of a specific metal can be considered in order to understand the influence of the coordination sphere in heteroleptic derivatives 15 or heterometallic precursors containing ligands tested prior in FEBID are evaluated.…”

Highly‐Packed Proximity‐Coupled DC‐Josephson Junction Arrays by a Direct‐Write Approach

“…Very recently, direct‐write printing of single Josephson proximity junctions was demonstrated by FEBID of tungsten carbide. [ 11 ] At the same time, the development of 3D superconducting sensor arrays and quantum networks requires the understanding of the physics of superconductor‐to‐metal transition (SMT) and charge transport regimes in closely‐packed JJA with tunable coupling strength.…”