Oriented Overgrowth of Evaporated Crystallites Fluoride Crystallites on Cleavage Surfaces of Single Crystals

概要

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The orientation of crystallites in fluoride films (LiF, NaF, CaF_2, MgF_2, AlF_3 and Na_3AlF_6)evaporated in vacuum onto the cleavage surfaces of several kinds of single crystals (galena, rocksalt, molybdenite and zincblende)were investigated by means of electron diffraction. The oriented overgrowth occurs even when the misfit is larger than 20%; for LiF and NaF on galena misfits are -33% and -23% respectively, for LiF on rocksalt misfit is -29% and for CaF_2 on molybdenite +23%. On the other hand, for CaF_2 on rocksalt the random orientation occurs though the misfit is only -3%. Therefore, the occurrence of orientation can not be predicted solely by the value of misfit .It is worth mentioning that in the present experiment no twin was observed provided the evaporated layer is thin, as previously stated by Uyeda [Proc. Phys. Math. Soc. Jap .26(1942)809]. This excludes the mechanism of oriented Overgrowth which was proposed bv .Menzer [Naturw. 26(1938) 385; Z. Krist .A99(1938)410]and later adopted by Frank and Merwe [Proc. Roy. Soc. A198(1949)205].
1956-03-05