Low-Energy Ion Scattering as a Probe of Correlated Electrons at Surfaces
Abstract
The incorporation of correlated electron phenomena into electronic devices is an important part of the effort to move technology beyond the limitations of silicon. Examples include conventional and high-temperature superconductors, Kondo systems, exotic magnetic systems, and colossal magnetoresistive materials. To fully exploit such phenomena, it is necessary to understand the fundamental physics and surface properties at the nanometer length scale. We have initiated a program in which low energy (0.5-5.0 keV) ions are used to investigate emergent phenomena at surfaces. We probe the local surface potential and electronic configuration through measurements of charge exchange and electron emission that occur during scattering. Because of the localized nature of their interaction with solids, ions are one of the most useful probes of surface composition and atomic structure. It has also been demonstrated that the inelastic interactions of ions with surfaces are sensitive to the local electronic configuration at the scattering site. In particular, ion neutralization is enhanced when the local surface work function decreases, and is conversely reduced when the local work function increases. This enables low energy alkali ion neutralization to serve as a probe of the local surface potential on an inhomogeneous material. For this abbreviated project, we applied the ion scattering technique to a few key correlated electron systems. We collected charge-state resolved time-of-flight spectra of the emitted atomic particles as a function of energy, angle and sample temperature. An analysis of the spectra provides the neutral fraction of alkali ions scattered from each particular atomic site on the surface. The neutralization is understood within the framework of the Resonant Charge Transfer (RCT) mechanism, which is applicable for any atomic particle with an ionization potential that overlaps states in the surface.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 11, 2009
- Accession Number
- ADA514408
Entities
People
- Jory A . Yarmoff
Organizations
- University of California, Riverside