CONTRAST OF COLLOIDAL GOLD PARTICLES AND THIN-FILMS ON A SILICON SUBSTRATE OBSERVED BY BACKSCATTERED ELECTRONS IN A LOW-VOLTAGE SCANNING ELECTRON-MICROSCOPE

The contrast of particles of colloidal gold in the backscattered elect ron mode of high-resolution low-voltage scanning electron microscopy i s of interest for the use as markers in surface labeling techniques of electron microscopical histochemistry. Monte Carlo calculations show a contrast maximum when the particle diameter is comparable with the e lectron range in gold, and the electron energy showing the maximum dec reases with decreasing diameter. The calculations are confirmed experi mentally by measuring the contrast of 40 nm particles of colloidal gol d and evaporated gold films on a silicon substrate for comparison.