LAUSR

Observation at low voltage using scanning electron microscopes (SEMs) enables the characterization of surface details on specimens on a nanometer scale and is widely used in science and industry. However, the energy width of the electron source restricts the spatial resolution of SEMs at low voltage, but it can be narrowed by lowering the work function of the emitter material. Here, we developed a cold field emitter using a cerium hexaboride single crystal (CeB6-CFE) as a monochromatic electron source. The work function of the CeB6 (310) plane was estimated to be as low as 2.25 ± 0.17 eV, and the energy width ranged from 0.17 to 0.26 eV for angular current densities ranging from 0.10 to 80 μA/sr. This energy width was 20% to 30% narrower than that of conventional W(310)-CFEs. Using the CeB6-CFE, the spatial resolution of the SEM at an acceleration voltage of 0.5 kV was improved by 11% compared with that of an SEM using the W(310)-CFE.