Electron Diffraction Study of Evaporated Face-centered Cubic Crystallites

Abstract

Germer and White (Phys. Rev. 60 (1941) 447) found that thin evaporated films of face-centered cubic metals produce electron diffraction patterns with anomalous intensities. Kimoto (J. Phys. Soc. Japan 8 (1953) 762) studied the anomaly by a trial method and attributed it to stacking faults in crystallites. By the radial distribution analysis the present author confirmed Kimoto's conclusion. Intensities of diffraction patterns from evaporated silver were accurately measured by the sector-microphotometer method and they were turned into radial distribution function. These functions reveal anomalous peaks caused by stacking faults. After a specimen is annealed at 350°C for 3.5 hrs., although crystallites do not grow remarkably, these peaks disappear. The amplitude of thermal vibration is found to be 0.15±0.02Å which agrees well with that for massive silver crystal. The narrowing of the first neighbor peak is found and is attributed to the correlative thermal vibration. Gold shows the same anomaly as is observed for silver, but aluminum shows no anomaly. These facts are in accordance with the value of stacking-fault energy.