Low temperature electrical characterisation of tungsten nano-wires fabricated by electron and ion beam induced chemical vapour deposition

Luxmoore, I. J.; Ross, I. M.; Cullis, A. G.; Fry, P. W.; Orr, Julie; Buckle, Philip Derek; Jefferson, J. H.

doi:10.1016/j.tsf.2007.02.029

Cited by 57 publications

(82 citation statements)

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“…Similar observation has been previously reported on the ion dose dependent growth of tungsten-containing materials by FIB [8]. High-resolution transmission electron microscope (HRTEM) measurements show that the tungsten-containing films grown by FIB do not display any long-range order [5], [6]. The dependence of the thickness on N s is shown in Fig.2.…”

Section: Resultssupporting

confidence: 85%

“…Disordered or granular W films alloys show significant T c enhancements [3]. The superconductivity of FIB-deposited tungsten was first demonstrated by Sadki et al [4] then by Luxmoore et al [5]. Both groups reported a Tc of 5.2 K for such material and qualitatively ascribe the comparatively high Tc to the absence of long-range order in the material crystal structure.…”

Section: Introductionmentioning

confidence: 98%

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Focused-Ion-Beam Direct-Writing of Ultra-Thin Superconducting Tungsten Composite Films

Fenton

Warburton

2009

IEEE Trans. Appl. Supercond.

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Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Abstract-Tungsten composite films of thickness as low as 19 nm have been deposited using a 30 keV Ga + focused-ion-beam with tungsten carboxyl (W(CO) 6 ) as the gas precursor. Films of thickness 25 nm or more are superconducting with a transition temperature exceeding 5 K. Films in the thickness range 25 nm to 50 nm show an increasing T c for a decreasing film thickness. This correlates well with the measured dependence of the normal state resistivity upon film thickness. We attribute this behavior to an increase in the BCS electron-phonon interaction potential resulting from a reduction in the electron mean-free-path as the film thickness is reduced. In the light of these data we discuss the applicability of FIB-deposited tungsten for devices requiring ultra-thin superconducting films, including photon detectors and phase-slip qubits.

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Section: Resultssupporting

confidence: 85%

Section: Introductionmentioning

confidence: 98%

Focused-Ion-Beam Direct-Writing of Ultra-Thin Superconducting Tungsten Composite Films

Fenton

Warburton

2009

IEEE Trans. Appl. Supercond.

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“…At this point it is worth mentioning that the conductivity can be further increased by employing focused ion beam induced deposition (FIBID) in combination with the precursor W(CO) 6 . Metallic tungsten-based FIBID structures which are also known to become superconducting below 5.2 K, [34][35][36][37] exhibit conductivity values up to 400-680 kS/m exceeding the values for tungsten-based FEBID structures reported here by a factor of 30-50 [34,36,38]. The difference of conductivity between samples prepared by means of FEBID and FIBID is, however, not inherent to deposits fabricated by the dissociation of W(CO) 6 .…”

Section: Resultscontrasting

confidence: 51%

Identifying the crossover between growth regimes via in-situ conductance measurements in focused electron beam induced deposition

Winhold¹,

Weirich²,

Schwalb³

et al. 2014

Nanofabrication

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Focused electron beam induced deposition presents a promising technique for the fabrication of nanostructures. However, due to the dissociation of mostly organometallic precursor molecules employed for the deposition process, prepared nanostructures contain organic residues leading to rather low conductance of the deposits. Post-growth treatment of the structures by electron irradiation or in reactive atmospheres at elevated temperatures can be applied to purify the samples. Recently, an in-situ conductance optimization process involving evolutionary genetic algorithm techniques has been introduced leading to an increase of conductance by one order of magnitude for tungsten-based deposits using the precursor W(CO)6. This method even allows for the optimization of conductance of nano-structures for which post-growth treatment is not possible or desirable. However, the mechanisms responsible for the observed enhancement have not been studied in depth. In this work, we identified the dwell-time dependent change of conductivity of the samples to be the major contributor to the change of conductance. Specifically, the chemical composition drastically changes with a variation of dwelltime resulting in an increase of the metal content by 15 at% for short dwell-times. The relative change of growth rate amounts to less than 25 % and has a negligible influence on conductance. We anticipate the in-situ genetic algorithm optimization procedure to be of high relevance for new developments regarding binary or ternary systems prepared by focused electron or ion beam induced deposition.

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“…[10][11][12][13][14][15][16][17][18] Such techniques enable the formation of metallic interconnects in a single 'writing' step, with a resolution comparable to structures defined by electron-beam lithography. Studies have been performed to explore the growth mechanism, [11,12] the transport properties [10,13,16] and their application in prototype device fabrication.…”

Section: Introductionmentioning

confidence: 99%

Tunability of the superconductivity of tungsten films grown by focused-ion-beam direct writing

Fenton

Wang

et al. 2008

Journal of Applied Physics

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We have grown tungsten-containing films by focused-ion-beam FIB -induced chemical vapor deposition. The films lie close to the metal-insulator transition with an electrical conductivity which changes by less than 5% between room temperature and 7 K. The superconducting transition temperature Tc of the films can be controlled between 5.0 and 6.2 K by varying the ion-beam deposition current. The Tc can be correlated with how far the films are from the metal-insulator transition, showing a nonmonotonic dependence, which is well described by the heuristic model of Osofsky et al. (Phys. Rev. Lett. 87, 197004 (2001)). Our results suggest that FIB direct-writing of W composites might be a potential approach to fabricate mask-free superconducting devices as well as to explore the role of reduced dimensionality on superconductivity.Keywords: Direct-writing, nanoscale structures, superconductivity, tungsten, focused-ionbeam deposition IntroductionThe investigation of enhanced superconductivity has been a major activity in solid-state physics and materials science in the last few decades. There are only 27 elements which, in bulk form, are superconductors at ambient pressure. The highest critical temperature, T c , of an elemental bulk material is that of niobium (T c = 9.3 K). Thus the search for higher-T c superconductors was expanded to alloys, compounds and composites. [1][2][3][4][5][6][7][8] In an alloy, the degree of order can be very important in determining the superconducting properties. For high transition-temperature superconductors the stoichiometric composition and the structural order are of great importance in obtaining a maximal T c . By contrast, highly disordered transition metals mostly display a higher T c than their annealed ordered counterparts. Tungsten is the superconductor of choice for fabrication of transition-edge sensors (TESs) for optical and near-infared wavelengths due to the tunability of its superconducting transition temperature in the range 100 mK and its relatively weak electron-phonon coupling at such temperatures.[9] Single-crystal tungsten has a very low transition temperature: T c of alpha (bcc) W is 15 mK and that of beta (A15) W is in the range 1 K to 4 K. Amorphous tungsten films [4][5] and alloys, [6][7][8] when rendered into a disordered or granular state, have a T c which can be up to two orders of magnitude larger than that of single-crystal bcc W.Recently the use of a focused ion-or electron-beam to induce the deposition of composite materials from metal-organic precursors has emerged as an important nanofabrication technique. [10][11][12][13][14][15][16][17][18] Such techniques enable the formation of metallic

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Low temperature electrical characterisation of tungsten nano-wires fabricated by electron and ion beam induced chemical vapour deposition

Cited by 57 publications

References 36 publications

Focused-Ion-Beam Direct-Writing of Ultra-Thin Superconducting Tungsten Composite Films

Focused-Ion-Beam Direct-Writing of Ultra-Thin Superconducting Tungsten Composite Films

Identifying the crossover between growth regimes via in-situ conductance measurements in focused electron beam induced deposition

Tunability of the superconductivity of tungsten films grown by focused-ion-beam direct writing

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