The direct recording of field ion micrographs by electrographic methods

Abstract

High-quality micrographs have been directly recorded within a dynamically pumped liquid nitrogen-cooled field ion microscope by electrographic methods. The image gas ions formed an electrostatic charge pattern on a receptor plate which was then developed with a fine-grained liquid developer of negative particle charge. Various receptor surfaces were tested, including insulating materials, semiconductive and photoconductive evaporated layers on aluminum substrates, and electrophoretically deposited zinc oxide-binder coatings on aluminum foil. Both helium and neon were used as image gases; the distance from tip to receptor plate was either 140 mm or 25 mm. The receptor layers A1203, amorphous selenium, and the zinc oxide-binder coating, provided the latter was given an initial negative charge, yielded developed images which showed excellent definition and resolution over the entire field. The exposure times for helium and neon images, other factors being the same, were closely comparable. Under the test conditions chosen, negatively charged zinc oxide-binder coatings on aluminum foil required the shortest exposure times-namely, 2 to 20 seconds at 25-mm tip-to-plate distance.