Lawrence Berkeley National Laboratory

Sub-Angstrom TEM of materials at intermediate voltages requires a sub-Angstrom information limit for the microscope. With a Scherzer resolution of 1.7 Angstrom, but a sub-Angstrom information limit, the one-Angstrom microscope (OAM) project at the NCEM is able to generate resolution below 0.8 Angstrom. Microscope information limit comes from damping of transfer by the temporal coherence. A major term contributing to temporal coherence is energy spread in the electron beam. We derive a new expression for the energy spread, and show how it can be measured from the result that is obtained using a standard electron spectrometer.