The dynamics of energy transfer in hyperthermal energy ion scattering from metal surfaces

Thesis/Dissertation · Fri Dec 31 04:00:00 EST 1993

OSTI ID:121190

DiRubio, C A

I have studied the interaction potential, energy transfer, and trapping for Na{sup +} scattering from a clean Cu(001) surface at incident energies ranging from 10 eV to 100 eV. Excellent agreement with the measured energy- an angle-resolved ion scattering distributions is achieved with simulations using a scattering potential consisting of a sum of Hartree-Fock (Na-Cu){sup +} pair potentials and an additional attrative potential to account for the classical image interaction. From these simulations detailed information about the scattering dynamics is extracted, such as the scattering trajectories, and energy transfer and trapping mechanisms. For energies below 100 eV we find that these quantities are particularly sensitive to the attractive well in the potential: the scattered angular distribution broaden, the fractional energy transfer increases, and the onset of trapping of the scattered flux is observed. The trajectories and energy transfer mechanisms leading to the trapping, and their dependence on incident energy are discussed. Differences between the energy and angular distributions that are consistent with a simple model in which the scattered Na{sup +}, unlike the Na{degrees}, is decelerated by the attractive well. Evidence for trajectory dependent neutralization is also presented and discussed. I have also studied the width of the peak in the energy spectra corresponding to single collisions between the ion and a CU surface atom for 50 eV to 400 eV Na{sup +} and 200 eV K{sup +} scattering. The width has been measured as a function of surface temperature, scattering geometry, and incident energy. The width, which is dominated by the momentum fluctuations of the surface atom, is in excellent agreement with a rigorous semiclassical calculation at high temperatures. At temperatures below the Debye temperature the zero point motion of the atom increases the peak width. I have observed evidence of this behavior at T{sub s} < 200K.

• Research Organization: Cornell Univ., Ithaca, NY (United States)
• OSTI ID: 121190
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
COPPER
ENERGY TRANSFER
ION-ATOM COLLISIONS
METALS
POTASSIUM IONS
SCATTERING
SODIUM IONS
SURFACES