A Retrofittable Photoelectron Gun for Low-Voltage Imaging Applications in the Scanning Electron Microscope

Low-voltage scanning electron microscopy is a powerful tool for examining surface features and imaging beam-sensitive materials. Improving resolution during low-voltage imaging is then an important area of development. Decreasing the effect of chromatic aberration is one solution to improving the resolution and can be achieved by reducing the energy spread of the electron source. Our approach involves retrofitting a light source onto a thermionic lanthanum hexaboride (LaB6) electron gun as a cost-effective low energy-spread photoelectron emitter. The energy spread of the emitter's photoelectrons is theorized to be between 0.11 and 0.38 eV, depending on the photon energy of the ultraviolet (UV) light source. Proof-of-principle images have been recorded using this retrofitted photoelectron gun, and an analysis of its performance is presented.