VACANCY ORDERING STRUCTURES IN EPITAXIAL RESI2-X THIN-FILMS ON (111)SI AND (001)SI

The vacancy ordering structures of epitaxial TbSi2-x, ErSi2-x, YSi2-x, and DySi2-x thin films on (001)Si and (111)Si have been investigated by electron diffraction analysis. From a combination of studying planv iew and cross-sectional transmission electron microscope samples, the 3-dimensional structures of vacancy ordering were determined. The vaca ncy ordering superstructure of unit cell (a root 3 a root 3 2c) was fo und in epitaxial TbSi2-x, ErSi2-x and YSi2-x thin films on (001)Si sam ples. However, the vacancy ordering superstructure of unit cell (a roo t 3 a root 3 c) was found in epitaxial TbSi2-x and DySi2-x thin films on (111)Si samples. The variation in strains induced in these films is suggested to result in the change of the vacancy ordering structure.