Multicharged Ion Research Facility (MIRF) in the Physics Division of Oak Ridge National Laboratory (ORNL) for a number of years now. The most recent research work has been focused on ion-surface interactions involving two main areas:

 

·         Study of charge-state distributions of multicharged ions in the low keV range, backscattered from metal and insulator surfaces.

·         Chemical sputtering of graphite resulting from very-low-energy (eVs) ion bombardment.

 

Measurements are performed in a floating potential ultra-high vacuum chamber with base pressures in the 10^-10 Torr range, shown schematically in Figure 1, into which decelerated ion beams from an ECR ion source are directed, as described in the article: Rev. Sci. Inst.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1: Schematic diagram of the decelerated beam surface scatttering apparatus.

 

 

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Charge-state distributions of multicharged ions

 

In the study of the interactions of slow highly charged ions with metal, semiconductor, and insulator surfaces in a binary collision, backscattering geometry, the goal is to improve fundamental understanding of neutralization and energy dissipation occurring in such interactions, and then to apply the knowledge gained to probe and modify the surfaces of single crystals, thin films, and nanostructures.

 

The large-angle backscattering technique has seen increased use in studies of multicharged ion (MCI) neutralization during interactions with solid surfaces (see several related articles). The use of MCI projectiles has been shown to significantly enhance the surface sensitivity of the backscattering technique (Phys. Rev. Letter article). Also, in contrast to grazing incidence studies where a large number of lattice sites are involved, large-angle backscattering measurements allow the resolution of interactions occurring with just one or two atoms located on the target surface (see Figure 2).