Heavy ion recoil spectroscopy of surface layers

Timo Sajavaara
Abstract & Cover

Determination of atomic concentration distributions in thin films is a key problem in materials science. The optimisation process of the thin film growth parameters in particular requires detailed information about the elemental concentrations of the main constituents and undesired impurities. So far, the characterisation methods capable of a depth-sensitive analysis of all elements have remained limited. In the research for this thesis, the concentration distributions of elements in surface layers were studied using heavy ion elastic recoil detection analysis (HI-ERDA). The analysis was expanded to include hydrogen and the heaviest elements. The energy-dependent detection efficiency of the time-of-flight energy telescope was determined for the lightest elements. The reliability of the concentration distributions obtained was seen to be strongly affected by the multiple scatterings of the ions and surface roughness of the sample. Both of them were studied by comparing Monte Carlo simulation results with the experimental ones. The surface topographies used in the simulations were determined with a scanning probe microscope. The analysis procedures developed were applied to characterise novel materials such as atomic layer deposited thin films used in future integrated circuit designs and pulsed vacuum arc deposited thin films, which are candidates for fusion reactor wall materials.

Source of Information
FinALD40 exhibition material, http://www.aldcoe.fi/events/finald40.pdf
University of Helsinki, Department of Physical Sciences, Accelerator Laboratory
(Helsinki, Finland)
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