Superconducting Materials and Devices Grown by Focused Ion and Electron Beam Induced Deposition

Abstract

Since its discovery in 1911, superconductivity has represented an equally inciting and fascinating field of study in several areas of physics and materials science, ranging from its most fundamental theoretical understanding, to its practical application in different areas of engineering. The fabrication of superconducting materials can be downsized to the nanoscale by means of Focused Ion/Electron Beam Induced Deposition: nanopatterning techniques that make use of a focused beam of ions or electrons to decompose a gaseous precursor in a single step. Overcoming the need to use a resist, these approaches allow for targeted, highly-flexible nanopatterning of nanostructures with lateral resolution in the range of 10 nm to 30 nm. In this review, the fundamentals of these nanofabrication techniques are presented, followed by a literature revision on the published work that makes use of them to grow superconducting materials, the most remarkable of which are based on tungsten, niobium, molybdenum, carbon, and lead. Several examples of the application of these materials to functional devices are presented, related to the superconducting proximity effect, vortex dynamics, electric-field effect, and to the nanofabrication of Josephson junctions and nanoSQUIDs. Owing to the patterning flexibility they offer, both of these techniques represent a powerful and convenient approach towards both fundamental and applied research in superconductivity.

Nanoscale direct-write fabrication of superconducting devices for application in quantum technologies

“…The fact that superconducting materials themselves can be directly grown by FEBID/FIBID represents an added value. Challenges here are the relatively high electrical resistance of the grown materials and the reproducibility of the composition and physical properties of the deposited materials [79]. (2) High-resolution superconducting resonators.…”

“…Since 2004, when superconductivity (T C = 5.2 K) was discovered in W-C deposits by FIBID using the W(CO) 6 precursor [75], a high number of publications have reported the use of FEBID and FIBID for growing superconducting structures, as recently reviewed in detail by our group [79]. The reader is invited to read that publication in order to find all types of reports on the topic, whereas here, we will focus on applications of superconducting deposits by FEBID and FIBID in the field of quantum technologies.…”

Molecular Electronics: Creating and Bridging Molecular Junctions and Promoting Its Commercialization

“…[151] Two significant characteristics of FEBID/FIBID are the high resolution and the flexibility in the shape of the grown nanostructures. [152] Wei et al applied the FEBID process in a scanning electron microscopy to narrow down the carbon nanotube (CNT) nanogaps in situ by decomposing the adsorbed organic vapor (toluene or ethanol) into carbon and then coating the surface of the CNT, [153] as shown in Figure 7E. The deposited sp 2 -rich amorphous carbon not only shrank the gap down to 2 nm, but also provided a π-conjugated surface which could link the molecules by a strong π-stacking interaction, hence forming carbon-molecule-carbon junctions.…”

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.…”

“…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 = 4–5 K, 25–28 an upper critical magnetic field of B c2 = 7–8.5 T 29–31 and a critical current density of J c = 0.01–0.1 MA cm −2 . 26–28 The London penetration depth is reported to be λ L = 850 nm 32,33 and the superconducting coherence length ξ = 6–9 nm.…”