ENERGY-FILTERING TEM AND ELECTRON ENERGY-LOSS SPECTROSCOPY OF DOUBLE STRUCTURE TABULAR MICROCRYSTALS OF SILVER HALIDE EMULSIONS

摘要

Composite Ag(Br,I) tabular microcrystals of photographic emulsions were studied by the combination of energy-filtering electron microscopy (EFTEM) and electron energy-loss spectroscopy (EELS) in conjunction with energy-dispersive X-ray (EDX) microanalysis. The contrast tuning under the energy-filtering in the low-loss region was used to observe more clearly edge and random dislocations, {11(1) over bar} stacking faults in the grain shells parallel to {11(2) over bar} edges and bend and edge contours. Electron spectroscopic diffraction patterns revealed numerous extra reflections at commensurate positions in between the Bragg reflections and diffuse honeycomb contours; these were assigned to the number of defects in the shell region parallel to the grain edges and polyhedral clusters of interstitial silver cations, respectively, Inner-shell excitation bands of silver halide were detected and confirmed by EDX analyses, i.e. the Ag N-2,N-3 edge at 62 eV (probably overlapped with the weak I N-4,N-5 edge at 52 eV and the Br M(4,5) edge at 70 eV), the I M(4,5) edge at about 620 eV, and the Br L(2,3) edge at about 1550 eV energy losses. Energy-loss near-edge structure of the Ag M(4,5) edge at about 367 eV energy losses and low-loss fine structure arisen as a result of interband transitions and excitons, possibly superimposed with many electron effects, have been revealed, The crystal thickness was determined by a modified EELS log-ratio technique in satisfactory agreement with measurements on grain replicas. [References: 58]