High-resolution and low-voltage FE-SEM imaging and microanalysis in materials characterization

Nanometer-resolution imaging in field-emission SEM (FE-SEM) instruments is now widely used in materials characterization. The use of a high-brightness field-emission gun and a high-resolution lens system makes it possible to acquire nanometer-resolution surface images at low voltages (<5 kV). The advantages of low-voltage FE-SEM include enhanced surface sensitivity, reduced sample charging for nonconducting materials, reduced damage of delicate samples, and significantly reduced electron range and interaction volume in bulk samples. For microanalysis using characteristic X-ray signals, the spatial resolution is significantly improved and the surface sensitivity is enhanced because of the fall of electron range at low voltages. With further development of high energy resolution X-ray detectors and probe-forming lenses, low-voltage imaging and microanalysis in FE-SEM instruments will be competitive both in spatial resolution and in chemical sensitivity to those now achievable in analytical TEM instruments. Applications of low-voltage SE imaging and microanalysis techniques to the study of various types of bulk materials are discussed.