Full-field XPS and UPS imaging at both high lateral (100 nm) and energy (100 meV) resolutions is becoming a reality with a new generation of energy-filtered photoelectron emission microscopes (PEEM) such as the NanoESCA [1]. PEEM offers an interesting alternative to scanning photoelectron microscopy (SPEM) in surface science as it allows real time imaging of surfaces and at much higher lateral resolutions. Energy-filtered PEEM is also complementary to Scanning Auger Microscopy, as it provides a variety of new contrast mechanisms otherwise not available, arising not only from surface topography, from local variations of work function (UV-PEEM), but also from local differences in elemental concentration and bonding state distribution (XPEEM). The NanoESCA is the first PEEM spectromicroscope with an aberration-corrected energy filter (double hemispherical analyzer) that allows to work at low pass energies (and therefore, high transmission) without detrimental effects on the spatial resolution. We used the first commercial NanoESCA instrument recently implemented in the Nanocharacterization Centre of CEA-MINATEC in Grenoble to perform high-resolution core-level and threshold photoemission imaging and nano-spectroscopy using various excitations sources : laboratory UV and x-ray sources, soft x-rays from the ID08 beamline at the ESRF [2]. In this contribution, we will focus on some of the recent applications in surface science demonstrated with UV- and XPEEM spectromicroscopy using the NanoESCA both in laboratory synchrotron environments. It includes local work-function contrast in polycrystalline copper and epitaxial semi-conducting layers (lateral resolution 40 nm) as well as elemental and chemical state contrast in electrografted polymers, copper-palladium surfaces, and cadmium-telluride-gold interfaces (lateral resolution 120 nm).
[1] M. Escher, N. Weber, M. Merkel, B. Krömker, D. Funnemann, S. Schmidt, F. Reinert, F. Forster, S. Hüfner, P. Bernhard, Ch. Ziethen, H. J. Elmers, G. Schönhense, J. Phys: Condens. Matter 17, 1329 (2005).
[2] O. Renault, N. Barrett, A. Bailly, L. F. Zagonel, D. Mariolle, J. C. Cezar, N. B. Brookes, K. Winkler, B. Krömker, and D. Funnemann, Surf. Sci. 2007, to be published.
|