The structures and variation of vacancy ordering in epitaxial DySi2-x thinfilms on (111)Si

Epitaxial DySi2-x films were grown in a-Si (15 nm)/Dy (30 nm)/(111)Si sampl es annealed at 700 degrees C for 10 min in an ultrahigh vacuum chamber. Fro m the electron diffraction pattern analysis, the structure of the epitaxial DySi2-x thin films were determined to consist of a superstructure of an ro ot 3 X root 3 R 30 degrees vacancy ordering structure with an out-of-step s tructure. The three-dimensional structure of the root 3 X root 3 R 30 degre es vacancy ordering was determined to be (root 3 X root 3 R 30 degrees 2c). The periodicity along the c-axis of the out-of-step vacancy ordering struc ture with M = 2 was also analyzed to be 2c. The intrinsic structure was fou nd to transform to various modulated structures by ion bombardment during c ross-sectional transmission electron microscope (TEM) sample preparation. ( C) 1999 Elsevier Science B.V. All rights reserved.