Unusual thickness dependence of the superconducting transition of -MoGe thin films
نویسندگان
چکیده
Thin films of -MoGe show progressively reduced Tc’s as the thickness is decreased below 30 nm and the sheet resistance exceeds 100 / . We have performed far-infrared transmission and reflection measurements for a set of -MoGe films to characterize this weakened superconducting state. Our results show the presence of an energy gap with ratio 2 0 /kBTc=3.8 0.1 in all films studied, slightly higher than the BCS value, even though the transition temperatures decrease significantly as film thickness is reduced. The material properties follow BCS-Eliashberg theory with a large residual scattering rate but the expected coherence peak seen in the optical scattering rate is lost in the thinner samples. This result cannot be explained within conventional theories.
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