Atomic Billiard – Materials Science using hyperthermal Ions

Ions and atoms are in their properties much alike. Except the electrical charge, which enables us to control the velocity and direction of ions in contrast to atoms in a fairly straight forward and precise way. Just the voltage of a ordinary car battery (12 V) can accelerate for instance an Ar+ ion to approximately 7.6 km/s – almost the velocity required to leave the earths orbit (1st cosmic velocity 11.2 km/s). If these fast projectiles impact on surfaces, their defined directionality and momentum provides for a game of billiard on smallest level possible. The extreme conditions of the collisions are widely utilized in materials science for unique analysis and non thermal synthesis methods, as for example just thermal excitation of Ar at room temperature (20°C) results in “only” 0.35 km/s.
The lecture will therefore introduce sources of ions and ways to control their energy and directionality (plasmas, accelerators, ion optics), with a short outlook on the underlying physics. Further, the basic principles of ion-surface interactions will be described and examples for their applications will be given, both for synthesis as well as analysis methods. For the first, thin film deposition and ion implantation methods, for the latter, ion-beam analysis methods, such as elastic recoil detection, Rutherford backscattering and nuclear reaction analysis, will be exemplarily elucidated.