Epitaxial growth and electrical conductance of metal (CoSi 2 )/insulator(CaF 2 ) nanometer-thick layered structures on Si(111)

Epitaxial growth of a metal (CoSi2) /insulator (CaF2) nanometer-thick layered structure on Si(111) was demonstrated and the resistivity of CoSi2 epilayer in this structure was investigated. An epitaxial CoSi2 layer on CaF2 was obtained by the two-step growth technique,i.e. solid phase epitaxy with the epitaxial Si layer grown in the first step and Co deposited in the second step. This technique was shown to be effective to avoid the Co agglomeration on CaF2 layer observed in the co-evaporation of Si and Co. An epitaxial CaF2 layer was formed on CoSi2/CaF2 at low substrate temperature (450°C) with partially ionized and accelerated CaF2 beam, to avoid Co agglomeration in the CoSi2/CaF2 underlayer as well. Obtained results showed a single-crystalline nature in reflection high-energy electron diffraction (RHEED) and transmission electron microscopy (TEM) observations. The resistivity of a few nm-thick CoSi2 epilayers embedded by CaF2 has been investigated. We studied thickness and annealing temperature dependence of resistivity and showed that a minimum resistivity of 30 μΩ cm was obtained in a 2 nm-thick CoSi2 sample annealed at 860°C.