Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 29: Poster session II (Nanostructures, Magnetism, Particles and clusters, Scanning probe techniques, Time-resolved spectroscopy, Structure and dynamics, Semiconductor surfaces and interfaces, Oxides and insulators, Solid-liquid interfaces)

O 29.58: Poster

Wednesday, March 29, 2006, 14:30–17:30, P2

Positron induced Auger electron spectroscopy — •Stefan Legl and Christoph Hugenschmidt — Technische Universität München, Lichtenbergstraße 1, 85747 München

Positron annihilation induced Auger electron spectroscopy (PAES) uses the annihilation of a positron with an electron of the inner shell of atoms whereas X-rays or high energy electrons are used in conventional AES for ionisation. Advantages of PAES are the higher surface sensitivity and the better signal to noise ratio. In order to benefit from PAES one has to use a low-energy positron beam of high intensity, which is available at NEPOMUC at FRM-II. However, the positron intensity amounts to a few picoampere whereas up to 1mA electron current is used in AES. To overcome this lack of intensity a novel time-of-flight spectrometer (TOF-PAES) was developed, which efficiently collects the emitted Auger electrons. In the TOF-PAES the energy of the Auger electrons is determined by the measurement of the electron flight time with an accuracy of 1eV. The detection of one annihilation quantum (511keV) delivers the start signal for the timing. After a flight of about 1.1m the Auger electron hits a micro channel plate detector which creates a stop signal. The features of this new spectrometer as well as first results will be presented.