Atomic-resolution imaging of lithium in Al3Li precipitates

Using an aberration-corrected transmission electron microscope, we report on imaging individual atomic columns of Li in the intermetallic compound Al3Li. The effect of electron energy on the imaging characteristic of Li is investigated by performing measurements at 80 kV employing a monochromated electron beam with an energy spread Delta E of 0.2 eV and at 300 kV with Delta E of 0.8 eV. These settings enable similar information transfer at both microscope operation conditions and allow a direct comparison between the 80 and the 300 kV measurements. Our experimental data show that the phase of the reconstructed exit-plane wave is highly sensitive to light atoms and that the displacement damage of light elements of low threshold recoil energy can be larger at 80 kV than at 300 kV. This behavior can be understood in terms of the relativistic elastic-scattering cross section between electrons and atoms.