CRYOELECTRON SPECTROSCOPIC IMAGING, ELECTRON-ENERGY-LOSS SPECTROSCOPYAND ENERGY-DISPERSIVE X-RAY-ANALYSIS OF AG(BR,I) NANOCRYSTALS AND MICROCRYSTALS

The combination of cryo-electron spectroscopic imaging (ESI)/electron energy-loss spectroscopy (EELS) and cryo-energy-dispersive X-ray (EDX) analysis in the scanning transmission (STEM) mode was applied for the characterization of Ag(Br, I) nano- and microcrystals. Combined quali tative silver and halide distributions were obtained by ESI (a three-w indow method) and by EDX/STEM including a high-magnification mapping o f nanocrystals. A low-loss fine structure in EEL spectra between 4 and 26eV was attributed to excitons and plasmons possibly superimposed wi th interband transitions and many-electron effects. Contrast tuning un der energy-filtering was used to image electron excitations in the sil ver halide particles. The real and imaginary parts, epsilon(1) and eps ilon(2), of dielectric permittivity were determined by means of a Kram ers-Kronig analysis. A proposed assignment of exciton peaks based on c alculations of electronic band structure of silver halides is discusse d.