Abstract: An electron microscope is described. This electron microscope includes an electron emitter that has an evaporation or sublimation rate that is significantly less than that of tungsten at the reduced pressures around the electron emitter during operation of the electron microscope. As a consequence, the electron microscope may be able to operate at reduced pressures that are much larger than those in existing electron microscopes. For example, at least during the operation the reduced pressure in the electron microscope may be greater than or equal to a medium vacuum. This capability may allow the electron microscope to use a roughing pump to provide the reduced pressure, thereby reducing the cost and complexity of the electron microscope, and improving its reliability. In addition, the size of the electron microscope may be reduced, which may enable a hand-held or portable version of the electron microscope.