Design and performance of a double-pass high-resolution electron energy loss spectrometer

The design, characterization, and performance of a high-resolution electron energy loss spectrometer for surface studies is described. The spectrometer is based on a double-pass 127° cylindrical deflector analyzer for both the monochromator and analyzer stages. An overall resolution of 4 meV is obtained with a current of 5×10−11 A measured at the sample. The resolving power of the double-pass deflector, in the specific geometry utilized, is significantly greater than that of either deflector. The observed energy resolution on metal and semiconductor surfaces is contrasted; it is found that electronic excitations lead to noninstrumental broadening on semiconductor surfaces.