Fabrication techniques for microdevices in soft superconductors

Rev. Phys. Appl. (Paris)

1979

We have studied devices consisting of 20 x 20 two dimensional arrays of proximity effect junctions of Au/In. The DC resistance at the origin as a function of temperature shows a transition at Tc (In) and another one at T*c, below Tc (In) but above Tc (Au/In). At T*c the devices go into a resistanceless state even though they are composed of SNS junctions. Different shapes of the current-voltage curves characterize each temperature region

“…Experimental. -The samples were made by application of a projection photolithographic technique developed by us [11]. A film of 230 A of gold is evaporated on a sapphire substrate.…”

mentioning

confidence: 99%

Finite size arrays of proximity effect bridges

Rev. Phys. Appl. (Paris)

1979

Properties of n × n square arrays of proximity effect bridges

1981

J Low Temp Phys

We have studied the I-V characteristics, the dc resistance at the origin R(T), and the critical current It(T) of arrays consisting of n • n (n = 10, 20, 30, and 40) In squares separated by Au/In regions. The superconducting squares have side ds(In) from 7.5 to 15 tzm and dN(Au/In) from 2.5 to 11 ~m. These devices show two transition temperatures in their R(T) curve; one at Tcc near Tc(In) and another one at T* above Tc(Au/In). The I-V curves for each temperature region resemble recent published results on NbN granular films. These arrays follow a formalism proposed by Wolf, Gubser, and Imry to describe the transition to a resistanceless state at T*. The measured values of I~(T) are larger than expected from n noninteracting Bardeen-Johnson functions in parallel, although the exponential behavior in temperature is followed. They are compatible with the idea of bands in the quasiparticle spectrum in the Au/In regions. Deviations in I~(T) from an exponential behavior in T near T* have been analyzed by applying to SNS arrays ideas developed for phase transitions in SIS arrays. Evidence that at T* we may be observing a phase transition at Tcj due to the Josephson coupling between In squares exists but it needs the development of theoretical work to be put on more solid grounds.

Size effects on the normal-state resistance of long microbridges

Weiss

Journal of Applied Physics

1979

We have calculated, within the Fuchs-Sondheimer approach, the effect on the normal-state resistivity introduced by the width in a long microbridge made in a thin film. It is shown that for bridges having widths smaller than about ten times the film thickness, their resistance increases. This result is in agreement with existing experimental results. We also discuss the role played by the effective bulk mean free path in relation to the film and bridge superconducting properties.