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 with A-15 type structure prepared by vacuum-deposition of tungsten. The size distribution of the crystals with the A- 15 type structure was ranged 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 structures generated at the same time in the initial stage of growth. The critical grain size of transformation from bcc to A-15 type structure was not observed in the nanometer-sized region. Coalescence of the nanometer-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 boundaries rotated by 30-degrees around the [100]A-15 axis. It was also implied from the observation that the A-15 structure in the present film was stabilized by some kinds of lattice defects.