Berlin 2015 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 23: Interfaces and Thin Films I (joint session CPP, DS)

CPP 23.9: Vortrag

Dienstag, 17. März 2015, 12:15–12:30, C 243

A Standing-Wave Approach in Ambient Pressure Photoemission: Chemical State and Depth Resolved Concentration Profiles of Solid/Liquid and Liquid/Gas Interfaces — •Slavomir Nemsak¹, Hendrik Bluhm², Charles Fadley³, and Claus Schneider¹ — ¹Peter Grünberg Institut 6, Forschungszentrum Jülich, 52425 Jülich, Germany — ²Chemical Sciences Division, Lawrence Berkeley National Laboratory, 94720 Berkeley, CA, USA — ³Department of Physics, University of California, 95616 Davis, CA, USA

A standing wave approach in the ambient pressure photoelectron spectroscopy is a new and powerful technique to study heterogeneous processes in solid/gas, liquid/gas and solid/liquid interfaces [1]. Advantages of the technique, such as superb depth resolution and chemical sensitivity, are demonstrated on several model systems with relevance to energy research, heterogeneous catalysis, electrochemistry, and atmospheric and environmental science. A strong standing-wave is generated using a multi-layer Si/Mo mirror as a substrate and phase of the standing wave is tailored through the interface of interest by rocking the sample around the Bragg angle. Photoemission signal from different species is then analyzed in order to provide their spatial arrangement, as well as local potential variations, along the direction perpendicular to the interface with sub-nm accuracy. Pros and cons of using harder X-ray excitation are discussed in terms of a photoemission signal strength and a standing wave effects amplitude.

[1] Nemsak et. al, Nature Communications 5, 2014.