Metastable impact electron emission microscopy: principles and applications

Metastable impact electron emission microscopy (MIEEM) provides a mesoscopic visualization of surfaces by electrons emitted owing to metastable He*‐atom (23S) impacts and a spectroscopic contrast by an imaging energy filter. Since the metastable He* atoms excite the outermost surface electrons solely, a high surface sensitivity is achieved. The MIEEM imaging mode was realized by the combination of the He* source with the spectroscopic low energy electron microscope (SpecLEEM), thus allowing a reliable tracing of spatiotemporal surface processes within the field of view of ca 50 µm diameter. A few examples of MIEEM‐applications are presented: a study of the chemical composition of insulating islands appearing on lanthanum‐doped SrTiO3(100) surfaces as well as the first successful employment of MIEEM for the in situ imaging of surface reactions. Copyright © 2006 John Wiley & Sons, Ltd.