AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeM

Paper SS2-WeM1
Enhanced Adatom Diffusion Using Glancing-Angle Ions

Wednesday, October 4, 2000, 8:20 am, Room 209

Session: Stimulated Surface Processes
Presenter: K.C. Ruthe, Northwestern University
Authors: S.A. Barnett, Northwestern University
K.C. Ruthe, Northwestern University
P.M. DeLuca, Kopin
Correspondent: Click to Email
We describe the effects of glancing incidence (3°) 3-4 keV Ar ion bombardment on homoepitaxial growth on vicinal GaAs (001). The average adatom lifetime on surface terraces was measured during GaAs deposition using specular ion scattering. The lifetime was observed to decrease monotonically with increasing ion current density, e.g. from 1.8 to 0.8 s for a current density increased from 0.6 to 22 mA/cm2 at a temperature of 520C (GaAs miscut = 2.5). There was no measurable sputtering, and the results suggested that the Ga surface diffusivity was increased by the ions. The ion beam also suppressed scattered ion beam current oscillations, suggesting that the growth mode had changed from two-dimensional island nucleation to step-flow due to increased adatom surface diffusivity. The RMS roughness of 0.3 micron thick GaAs epitaxial layers, measured by atomic-force microscopy, showed a corresponding decrease from 0.5 to 0.25 nm due to ion bombardment. A simple model, involving direct momentum transfer from ions to adatoms parallel to the surface, is shown to be consistent with the measured diffusion enhancements.