Another application of the magnetic beam system was the positron work function measurement from an energy analysis of the re-emitted positrons when the surface was bombarded with keV positrons. Forum Materials Sci. Preliminary measurements on a model system have demonstrated that PAES is able to identify sites of preferential adsorption. This indicates that the positrons are being pushed away from the Si but not the Au due to selective adsorption of oxygen at exposed Si sites. A schematic drawing indicating this mechanism is shown in this Figure.
Circles represent raw data, solid line is smoothed data.
PAES shows a very clean M23M4M4 transition peak. The energy differnece between the M2M4M4 peak and the M3M4M4 peak is about 5eV which is the same as expected from the free atomic model. To figure out the M2M4M4 peak and the M3M4M4 peak in detail, we compared the PAES data with the EAES data and optimized the peaks using Gaussian functions. V sample bias. Our system will differ from the pulsed beam system of Suzuki et al. in that it will make use of a DC positron beam and will rely on the detection of annihilation gamma rays with a BaF2 detector to provide a timing signal.