Growth and Characterization of Epitaxial Insulating CaF2 Layers on Silicon by MBE

In the course of the present work CaF₂ epitaxialfilms were grown on Si(111) substrates by means ofMBE. The Si substrates were chemically cleaned priorto insertion into the system. The final volatile oxidewas desorbed in situ by heating to 850. CaF₂ was evaporated from aKnudsen-type cell by use of a graphite crucible, whilethe growth temperature was held at 650 .RHEED (Reflection High Energy Electron Diffraction)has been used to monitor the film growth in situand to study the epitaxial quality. Also we have usedthe MeV He⁺ RBS channeling technique to look atdefects and to measure strain in the CaF₂ layer.Usually good crystallographic properties are achievedunder optimum growth conditions, with values of_min < 5%. Electrical properties aremeasured by use of a special MIS structure.