The electrical conductivity of polycrystalline ternary thin films of NbN(Ti) has been investigated to explore the effects of superconducting fluctuations. The temperature dependence of the conductivity has been found to be in agreement with the predictions of mean-field theory above the mean-field transition temperature with distinct temperature regimes corresponding to the 2-D and 3-D forms of the theory being observed.
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THE GENERAL features of the electrical conductivity of a superconductor above T, can be explained by the essentially phenomenological Ginzburg—Landau theory’ or mean field theory. Although this subject has been studied inten-sively2 there is no unambiguous experimental support for a major prediction of the theory, the transition from 2—D to 3—D behavior in films of intermediate thicknesses.3 In this letter we report the observation of this transition4 in disordered polycrystalline films of NbN(Ti), a high 1, material which has a broad transition to the * Supported in part by the U.S. Atomic Energy Commission under contract AT(11—1)—1959 (Physics) and by the Air Force Office ot Aerospace Research (Materials Science).
Acknowledgements — The authors would like to thank Y. M. Shy for preparation of films, J. Zbasnik for his assistance in the early part of the work and Paul Steinback for assistance with computations. One of the authors (FMS) would like to acknowledge the hospitality and support of the Ames Laboratory of the U.S. Atomic Energy Commission at Iowa State University where part of this work was carried out.