Secondary-Electron imaging by Scintillating Gaseous Detection Device

Abstract

The environmental scanning electron microscope (ESEM) incorporates the functions of the conventional SEM while it has the added capability of allowing the examination of virtually any specimen in a gaseous environment. The main modes of imaging are all represented in the ESEM, and some developments with regard to the secondary electron (SE) mode are reported herewith.The conventional E-T detector fails to operate in the gaseous conditions of ESEM, but this obstacle has been overcome with the advent of a gaseous detection device (GDD). The principle of operation of this device is based on the monitoring of the products of interaction between signals and gas. Initially, the ionization from the signal/gas interaction was used to produce images of varying contrast and, later, the gaseous scintillation, from the same interaction, was also used to produce images. First, a low bias was applied to various electrodes but later a much higher bias was used for the purpose of achieving additional signal gain. By careful shaping and positioning the respective electrode, it was shown that SE imaging is possible in the ESEM. This has been also independently demonstrated by use of a special specimen preparation.