Heteroepitaxial CaF2/Si and Si/CaF2/Si structures have been formed by conventional vacuum deposition of CaF2 and Si. Optimum conditions for obtaining good epitaxial films have been investigated by changing Si substrate orientations, film thicknesses, and substrate temperatures during film deposition. It has been found from Rutherford backscattering and channeling spectroscopy (RBS) that the crystalline quality of CaF2 films grown on Si (111) and (110) substrates is excellent, but that the quality of the films on Si (100) is much worse. It has also been found from RBS and TEM (transmission electron microscopy) that single-crystalline Si films are formed on the CaF2/Si (111) structure at substrate temperature of 700C. Finally, etching characteristics ofCaF2 and Si films have been studied. It has been shown that the CaF2 and Si films are selectively etched by the wet and dry plasma processes.
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