Motion of Electrons and Holes in Photographic Emulsion Grains

TLDR

Simultaneous light and voltage pulses are used to investigate how electrons and holes move within photographic emulsion grains and contribute to latent image formation. The study analyzes the characteristics of the light and voltage pulses applied during exposures to relate them to electron displacement within the grains. Electron micrographs reveal that conduction electrons are displaced by the electric field and become trapped within the grain surface in less than 1 µs, while evidence suggests that positive holes are mobile at the print‑out level but their displacement at the latent‑image level remains unconfirmed.

Abstract

The use of simultaneous pulses of light and voltage to study the motion of electrons and holes in photographic grains and the role played by these charge carriers in the formation of the latent image is discussed. The electric field displacement of conduction electrons forming print-out as well as latent-image silver is shown by electron micrographs of the grains. Also, results on the motion of positive holes are presented. It is possible to show at the print-out level that this carrier is mobile; although it may be that the hole is displaced at the latent-image level, this behavior has not been demonstrated. The light and voltage pulses used for the exposures are analyzed and related to electron displacement. Indications are that when electrons are forced to the grain surface by an electric field, they are trapped in a time less than 1 μsec.