GROWTH OF FINE CRYSTALS WITH A-15 TYPE-STRUCTURE IN VACUUM-DEPOSITED TUNGSTEN FILMS STUDIED BY HIGH-RESOLUTION ELECTRON-MICROSCOPY

High-resolution electron microscopy was performed on fine crystals wit h A-15 type structure prepared by vacuum-deposition of tungsten. The s ize distribution of the crystals with the A- 15 type structure was ran ged from 2 to 11 nm and was similar to that of the bcc type structure coexisting in the film, indicating that the nucleation of both structu res generated at the same time in the initial stage of growth. The cri tical grain size of transformation from bcc to A-15 type structure was not observed in the nanometer-sized region. Coalescence of the nanome ter-sized crystals with A-15 type structure was observed in the film. It was found that the crystals were connected by stacking faults with displacement vector of 1/2[100] and nanometer-sized tilt grain boundar ies rotated by 30-degrees around the [100]A-15 axis. It was also impli ed from the observation that the A-15 structure in the present film wa s stabilized by some kinds of lattice defects.