Untitled - IAP/TU Wien - Technische Universität Wien
Untitled - IAP/TU Wien - Technische Universität Wien
Untitled - IAP/TU Wien - Technische Universität Wien
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71st IUVSTA Workshop<br />
Secondary-Electron Electron-Energy-Loss Coincidence Measurements<br />
on Polycrystalline Aluminum<br />
Alessandra Bellissimo, 1,* Wolfgang S.M. Werner, 2 F. Salvat-Pujol, 3 Rahila Khalid, 4<br />
Mihaly Novák 5 and G. Stefani 6<br />
Institut für Angewandte Physik, Vienna University of Technology, Wiednerhauptstraße 8-10/134, A-1040, Vienna, Austria<br />
*bellissimo@iap.tuwien.ac.at<br />
The double-differential secondary electron-electron energy loss coincidence spectrum of Al<br />
has been measured for 100 eV primary electrons and energy losses between 0–25 eV. This energy<br />
loss range comprises the simple scattering regime of energy losses and therefore allows one to<br />
gain unique insight in the creation of secondary electrons (SE) in the course of excitation of<br />
single surface and bulk plasmons in Al.<br />
The experiment was performed in a UHV-system containing a hemispherical mirror<br />
analyser (HMA) for the detection of the fast backscattered electrons and a time-of-flight (TOF)<br />
spectrometer with an acceptance angle of approximately 2! for the slow secondaries, which are<br />
detected in coincidence with the backscattered primaries.<br />
The acquired double-differential coincidence spectra show very specific regions<br />
corresponding to different excitation processes. In the low-energetic loss region - between the<br />
work function delimitation and the bulk plasmon energy – the energy losses can be entirely<br />
attributed to surface excitations, where also contributions of super-surface scattering can be<br />
identified.<br />
At the energy loss corresponding to the bulk plasmon excitation, a sudden and unexpected<br />
transition can be observed, leading to a decrease of intensity. This is due to the increment of<br />
depth range where the SE are emitted from. The region beyond the bulk plasmon characteristic<br />
energy loss is dominated by the multiple inelastic scattering regime. The remarkable similarity of<br />
coincidence TOF-spectra for the energy loss range 0–25 eV with the single TOF-spectra shows<br />
that the main difference in the cascade regime is caused by the multiple excitations of bulk<br />
plasmons. Consequently, through the analysis of the SE spectrum measured in coincidence with<br />
surface and bulk plasmon losses a much more detailed picture concerning the contribution of<br />
plasmon decay to the emission of secondaries can be attained.<br />
References<br />
[1] W.S.M. Werner, F. Salvat-Pujol, W. Smekal, R. Khalid, F. Aumayr, H. Störi, A. Ruocco and<br />
G. Stefani, Appl. Phys. Lett. 99, 184102 (2011)<br />
[2] Wolfgang S.M. Werner, Mihaly Novák, F. Salvat-Pujol, Josef Zemek and Petr Jiricek,<br />
Phys. Rev. Lett. 110, 086110 (2013)<br />
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