Characteristics of superconducting tungsten silicide WxSi1−x for single photon detection

X. Zhang; A. Engel; Q. Wang; A. Schilling; A. Semenov; M. Sidorova; H.-W. Hübers; I. Charaev; K. Ilin; M. Siegel

doi:10.1103/PhysRevB.94.174509

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Characteristics of superconducting tungsten silicide WxSi1−x for single photon detection

X. Zhang, A. Engel, Q. Wang, A. Schilling, A. Semenov, M. Sidorova, H.-W. Hübers, I. Charaev, K. Ilin, M. Siegel

DOI 10.1103/PhysRevB.94.174509 · Physical Review B

T1

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Abstract

Superconducting properties of three series of amorphous WxSi1−x films with different thickness and stoichiometry were investigated by dc transport measurements in a magnetic field up to 9 T. These amorphous WxSi1−x films were deposited by magnetron cosputtering of the elemental source targets onto silicon substrates at room temperature and patterned in the form of bridges by optical lithography and reactive ion etching. Analysis of the data on magnetoconductivity allowed us to extract the critical temperatures, superconducting coherence lengths, magnetic penetration depths, and diffusion constants of electrons in the normal state as functions of film thickness for each stoichiometry. Two basic time constants were derived from transport and time-resolving measurements. A dynamic process of the formation of a hotspot was analyzed in the framework of a diffusion-based vortex-entry model. We used a two-stage diffusion approach and defined a hotspot size by assuming that the quasiparticles and normal-state electrons have the same diffusion constant. With this definition and these measured material parameters, the hotspot in the 5-nm-thick W0.85Si0.15 film had a diameter of 107 nm at the peak of the number of nonequilibrium quasiparticles.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
NbN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	10.5	Pressure not reported	unknown
NbTiN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	9.5	Pressure not reported	unknown
NbSi Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2	Pressure not reported	unknown
TaN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8	Pressure not reported	unknown
W0.75Si0.25 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.86	Pressure not reported	midpoint
W0.75Si0.25 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.88	Pressure not reported	midpoint
W0.8Si0.2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	4.02	Pressure not reported	midpoint
W0.8Si0.2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	4.08	Pressure not reported	midpoint
W0.85Si0.15 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.83	Pressure not reported	midpoint
W0.85Si0.15 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.85	Pressure not reported	midpoint