Epitaxial growth and electrical conductance of metal(CoSi₂)/insulator(CaF₂) nanometer-thick layered structures on Si (111)

Abstract

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.