The HPXPS Instrument at MAX-lab : a Powerful Tool for In Situ Catalysis Investigations

University essay from Lunds universitet/Fysiska institutionen; Lunds universitet/Synkrotronljusfysik

Author: Niclas Johansson; [2012]

Keywords: XPS; LEED; HPXPS; trilayer; FeO; Physics and Astronomy;

Abstract: A new instrument for near ambient x-ray photoelectron spectroscopy investigations of surfaces has been installed at beamline I511 of the MAX-II electron storage ring at the MAX IV Laboratory. This high pressure x-ray photoelectron spectroscopy instrument is capable of surface chemistry investigations in near ambient pressures using x-ray photoelectron spectroscopy (XPS), a technique that traditionally is limited to ultrahigh vacuum. To test the instrument, a trilayer iron oxide film was grown with O$_2$ pressures in the mbar regime. The growth was monitored \emph{in situ} with XPS, an experiment which is not found in the literature. The XPS fingerprint of the trilayer FeO$_2$ film was characterised in UHV, and consists of two major peaks in the O 1s spectrum and the peaks were assigned to its respective O species. The oxidation of CO over Pt(111) surface was also investigated using the HPXPS instrument. The oxidation process was observed with a quadrupole mass spectrometer in coincidence with the \emph{in situ} XPS measurements, showing the possibility to measure reactivity using the setup. In this thesis, the basics of the experiment methods are presented and the high pressure instrument is described in detail. Further, the structures and growth of the different FeO films are discussed on the basis of my own XPS and low energy electron diffraction (LEED) results and the data available in the literature.

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