The NSF Faculty Awards for Women Scientists and Engineers recognizes the high quality of the awardee's record in teaching and scholarship, as well as potential research, the academic profession, and the education of future scientists and engineers. Dr. Cooper's research under this award is directed at understanding the interactions of energetic ion beams with clean and adsorbate- covered single crystal metal surfaces. The dynamics of hyperthermal ion-surface scattering (incident energies below 500 eV) are of fundamental interest because it is in the hyperthermal energy regime that the transition occurs from thermal scattering,in which the ion interacts simultaneously with the entire surface to keV scattering, where the ion undergoes a series of sequential binary collisions with individual surface atoms. Hyperthermal scattering dynamics are also of practical importance since this energy regime is used in technological applications such as reactive ion etching and ion beam assisted epitaxy. To study these dynamics, well-characterized ion beams are scattered from clean and adsorbate-covered metal surfaces. Particular emphasis is placed on understanding aspects of the scattering dynamics, such as energy transfer to the surface and particle trapping, and on understanding mechanisms of ion-surface charge transfer. The initial studies will use alkali ion beams since the relative simplicity of alkali ion-surface reactions permits detailed modeling of the scattering and charge transfer dynamics. Scattering dynamics studies are currently underway for Na+ scattering from Cu(001), and will be extended to other alkalis and to other beam species, such as oxygen and nitrogen. Investigations to determine the mechanisms of ion-surface charge transfer are currently underway for incident Li+, Na+, and K+. They will be extended to other incident species, in particular atomic and molecular oxygen. A probe that is complementary to ion scattering for studying local atomic and electronic surface properties is the scanning tunneling microscope (STM). STM will be used in ultra high vacuum to study tunneling mechanisms on metal surfaces, the effect of adsorbates on the electronic structure at metal surfaces, and diffusion on metal surfaces.
