Electronic interactions of medium-energy ions: Recent results and their implications for high-resolution depth profiling
- Speaker: Daniel Primetzhofer
- Institution: Physics, Department of Physics and Astronomy, Uppsala University, Sweden
- Date: 12.5. 2017
- Place: CEITEC Brno University of Technology
Medium Energy Ion Scattering (MEIS) features unique material characterization capabilities:
Depth profiling of the elemental composition of a sample at length scales on the order of one
nanometer can be achieved, typically with virtually no sample damage. Additionally, information on
surface and near-surface crystallinity of single crystal sample becomes accessible. At Uppsala
University we have constructed a Time-Of-Flight (ToF-) MEIS set-up  featuring a large-area
position-sensitive detector coupled to an ion implanter as an ion source which is capable of
producing beams with high currents for many different ion species.
To fully exploit the analytical potential of MEIS, precise and accurate knowledge of electronic
interactions at the employed keV ions is necessary. Data is often found scarce and predictions
rely on extrapolations from higher energies. Additionally, compounds are rarely studied, in a
regime where simplifications from higher energies will have to be abandoned, and sample chemistry
may impact ion solid interaction. ToF-MEIS features, in combination with other ion-beam
analytical techniques a convenient tool to study ion-solid interaction at keV energies, which is
essential for quantification of data in many research areas such as ion implantation,
nanofabrication using ion beams or fusion research aside the beforehand mentioned depth profiling.
In parallel the data is of interest from a fundamental perspective yielding inside important in the
dynamics of strongly perturbed systems and thus a challenging playground for theory.
In the present contribution two exemplary systems, HfO2 and TiN have been investigated by
ToF-MEIS. HfO2 is known as a thin film gate-dielectric in solid state electronics, TiN is well known
as a hard coating but gains increasing popularity in electronical applications as e.g. diffusion
barrier. As a result, towards lower energies, deviations in the energy dependence of the electronic
energy loss are observed, with increasing effects for lower energies and heavier ions. Data also
indicate that static theoretical descriptions are insufficient to describe the observed magnitude
of electronic stopping for ions heavier than protons.