SUPERCONDUCTIVITY OF TUNGSTEN SILICON MULTILAYERS

Tungsten-silicon multilayers were prepared by electron beam deposition in ultrahigh vacuum. The number of bilayers and their thicknesses were 10 and 2-24 nm, respectively. Structural properties were analyzed by low and large angle X-ray diffraction and TEM. Tungsten films in multilayers were amorphous for the layer thickness d(w) less-than-or-equal-to 4 nm. Multilayers with d(w) = 1 and 2 nm were superconducting with T(c) = 2.72-4.21 K. Superconductivity was preserved in samples annealed up to 650-degrees-C for 40 s. At higher annealing temperatures the formation of crystalline tungsten silicides was observed, simultaneously the periodicity of multilayers was destroyed and superconductivity was lost.