Quantitative Evaluation of Charging on Amorphous SiO₂ Particles by Electron Holography

Abstract

The amount of the electric charge in spherical SiO₂ particles with 1 \\micron diameter has been evaluated quantitatively by using electron holography. The charging effect was found to depend on not only the incident electron intensity but also the insertion of an objective aperture. The amount of the electric charge in a SiO₂ particle is estimated to be 1.5×10⁻¹⁶ C under the current density of incident electron beam at 0.5 A/m² without an objective aperture. This electric charge is equal to the net loss of about 940 electrons from the amorphous SiO₂ particle. In the case of inserting an objective aperture, the amount of the electric charge on SiO₂ particles decreases by 30–40%. The results are compared with the cases of Au coated particles and the small particles of 250 \\micron in diameter.