30-kV spin-polarized transmission electron microscope with GaAs-GaAsP strained superlattice photocathode

A spin-polarized electron beam has been used as the probe beam in a transmission electron microscope by using a photocathode electron gun with a photocathode made of a GaAs-GaAsP strained superlattice semiconductor with a negative electron affinity (NEA) surface. This system had a spatial resolution of the order of 1 nm for at 30 keV and it can generate an electron beam with an energy width of 0.24 eV without employing monochromators. This narrow width suggests that a NEA photocathode can realize a high energy resolution in electron energy-loss spectroscopy and a longitudinal coherence of 3 x 10(-7) m. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737177]