Evolution of vacancy ordering and defect structure in epitaxial YSi2−x thin films on (111)Si

Abstract

The evolution of vacancy ordering and defect structure in epitaxial YSi2−x thin films on (111)Si have been studied by both conventional and high-resolution transmission electron microscopy. Epitaxial YSi2−x with an ordered vacancy structure was grown on (111)Si by rapid thermal annealing. In samples annealed at 500 °C for 120 s epitaxial YSi2−x was found to form. After annealing at 600 °C for 15 s, the appearance of additional diffraction spots is attributed to the formation of an ordered vacancy superstructure in the epitaxial YSi2−x thin films. In samples annealed at 600 °C for longer time or higher temperatures, the splitting of extra diffraction spots is correlated to the formation of an out-of-step structure. Streaking of the split diffraction spots in the diffraction pattern is attributed to the presence of an out-of-step structure with a range of M values. The M was found to settle down to 2 after high-temperature and/or long time annealing. Planar defects in YSi2−x films were analyzed to be stacking faults on {101̄0} planes with 1/6 〈1̄21̄3〉 displacement vectors. Computer simulation was carried out to determine the atomic structure of stacking fault. The simulated images are seen to match rather well with experimental images taken under two different values of defocus.