Characterization of Double Structure Tabular Microcrystals of Silver Halide Emulsions by Means of Electron Energy-Loss Spectroscopy, Zero-Loss Electron Spectroscopic Imaging and Energy-dispersive X-ray Microanalysis

Abstract

Electron energy-loss spectroscopy (EELS) and zero-loss electron spectroscopic imaging (ZLESI) in conjunction with spot energy-dispersive X-ray microanalysis (EDX) were applied to the structural and chemical characterization of practical emulsion core (AgBr)-shell (AgBr1-x Ix) tabular microcrystals. The samples were cryocooled to minimize damage under the electron beam. Recorded energy-loss spectra of the crystals in the initial state and after a 2-minute development contained several low intensity bands, which were tentatively assigned to silver and halides, as well as bulk, surface and defect plasmons and interband transitions. Spatially resolved energy-loss spectra of silver specks on extractive carbon replicas of silver halide grains showed the presence of the delayed Ag M4, 5edge at 400 eV Results of EELS-microanalysis have been confirmed by EDX spot analysis of the same emulsion samples. The improved contrast in the ZLESI mode enabled the detection of dislocation grid and stacking faults on the tabular grains as well as the visualization of the morphology and defect structure of silver filaments formed during development of microcrystals. Zero-loss filtering was also used to obtain high-resolution point diffraction patterns of the crystals with low background, containing extra reflections at commensurate positions in between the Bragg reflections probably due to a number of defects in the shell region.