SEM for the 21st Century: Scanning Ion Microscopy

The scanning electron microscope (SEM) has become the most widely used of all advanced imaging tools because it offers a unique range of capabilities. It can resolve and image objects with sizes ranging from millimeters to below 1 nm; it offers multiple ways to generate, collect, and display signals; the images produced contain information about the topography, chemical composition, and the magnetic, electrostatic, and crystallographic properties of the sample; and it can generate characteristic x-ray emission from the specimen to provide a quantitative chemical analysis. Unfortunately, one thing that it will be unable to do is maintain its competitive edge in the 21st century. This is because electrons are electromagnetic ‘‘waves’’ and thus the smallest spot, ‘‘d,’’ into which an electron beam can be focused has a diameter of the order of: d 1⁄4 k=a ð1Þ