Low-temperature transport properties of ultrathin CoSi2 epitaxial films

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Abstract
Low-temperature transport measurements (down to 18 mK) are performed in CoSi2 ultrathin films (down to 1.4 nm) epitaxially grown on silicon substrates. The low-temperature residual resistivity exhibits little dependence on the CoSi2 film thickness down to 10 nm. However, a steep increase is found below 10 nm, which is not taken into account by the Fuchs–Sondheimer [Proc. Cambridge Philos. Soc. 34, 100 (1938)] boundary scattering theory. Correlatively, the superconducting critical temperature of these CoSi2 films is abruptly depressed in the same thickness range. These two effects are phenomenologically explained by the presence of a perturbed layer, i.e., a CoSi2 interfacial layer in which the electronic transport properties are dramatically diminished.