Secondary Ion Imaging with a CCD Camera

Abstract

A digital image processing system based on a charge-coupled device (CCD) camera interfaced to a Texas Instruments Professional Computer (TIPC) has been implemented on the Cameca IMS-3F Ion Microscope to improve lateral imaging capabilities. The CCD sensor, produced at TI, generates a 376 × 288 pixel image, and a hardware interface to the TIPC provides an 8-bit grayscale (256 levels) for subsequent storage and display. The Cameca ion microscope projects secondary ions from the sample onto a microchannel plate/fluorescent screen combination. The CCD array images the screen directly and no vacuum modifications to the Cameca are required. Nitrogen cooling of the CCD imager to reduce thermal noise allows low light levels to be integrated for several minutes and displayed on the TIPC, providing a substantial increase in sensitivity over the standard optics. False color imaging enhances the contrast of various features in the ion image to provide ease of identification. A variety of software options, such as frame mosaicking, multiple frame overlays, color threshold modification and histogram equalization are available. The TIPC has also been interfaced to the Cameca controlling computer to allow display of ion images during depth profiling.