Quantum transport of buried single-crystallineCoSi2layers in (111)Si and (100)Si substrates

Magnetoresistance data for clean crystalline ${\mathrm{CoSi}}_2$ layers were analyzed in terms of weak localization, Coulomb interactions, and superconducting fluctuations. The ${\mathrm{CoSi}}_2$ layers with thicknesses of 11.5 nm in (111)Si and 23 nm in (100)Si were fabricated by high-dose ion implantation and subsequent annealing in a rapid thermal annealer (known as ion-beam synthesis or mesotaxy). The magnetic-field dependence of the resistance is interpreted in terms of two-dimensional weak localization with strong spin-orbit interaction and an addtional classical contribution proportional to ${\mathrm{H}}^2$. No indication of magnetic scattering was found, which is a sign of the ‘‘cleanness’’ of the samples. Long phase-coherence lengths of ${\mathit{l}}_{\mathrm{\phi }}$≊0.75 μm in (111)Si and ${\mathit{l}}_{\mathrm{\phi }}$≊2.3 μm in (100)Si at 4.2 K were determined by fitting the magnetoresistance data. The inferred inelastic-scattering time is interpreted as a sum of a clean-limit electron-electron process (dominant at temperatures below ≊6 K) and an electron-phonon process dominant at higher temperatures. We further observed a general orientation dependence of the electrical transport properties of mesotaxial ${\mathrm{CoSi}}_2$ layers, such as anisotropy in the residual resistance, Hall coefficient, and the prefactor for the classical ${\mathrm{H}}^2$ dependence of the magnetoresistance. This is probably related to multiple-band effects in ${\mathrm{CoSi}}_2$.