Simultaneous Collection and Processing of Energy-Filtered Images in Stem Using a Fast Digital System

Abstract

Hardware and software have been developed allowing concurrent acquisition of up to three electron energy-loss images formed by monitoring three separate regions of the energy-loss spectrum. This imaging mode provides display of three elemental contour maps or, after some digital image processing, an elemental contour map stripped of its spectrum background.Other systems proposed for simultaneous collection of these signals have not been realized because of the difficulties involved in manufacture of multiple parallel detectors consistent with the physical dimensions of the energy-loss spectrum. The technique described here requires just the single standard bright-field detector. The experimental apparatus consists of a Vacuum Generator's HB5 Scanning Transmission Electron Microscopy (STEM) under the control of a Fast Digital Acquisition System (FDDAS). A PDP11/34 minicomputer controls the electrostatic deflectors at the spectrometer exit so the spectrum can be shifted across the detector slits (Fig. 1). Circuitry enabling this has been incorporated directly into the FDDAS as an expansion device resident on the system bus.