Perspective on atomic-resolution vibrational electron energy-loss spectroscopy

Instrumentation developments in electron energy-loss spectroscopy in the scanning transmission electron microscope one decade ago paved the way for combining milli-electron volt energy resolution in spectroscopy with Ångström-sized electron probes, unlocking unexplored realms for solid state physics at the nanometer scale. The fundamental understanding of the scattering processes involved has made it possible to separate atomically localized signals, providing insight into vibrations at the atomic scale. In this Letter, we outline the experimental, conceptual, and theoretical advances in this field and also make comparisons with tip-based optical techniques before discussing future perspectives of this exciting method. Optimization of dark-field signal collection will play a fundamental role in making this technique more widely applicable to a range of material problems. The benefits of adding momentum-resolution will also be discussed, and a powerful acquisition scheme will be proposed.