Defect generation due to the very low-energy bombardment of (001) was studied. The Ar+ bombardment was performed using energies of between 20 and 95eV, and current densities of 0.1 to 0.75mA/cm2, on surfaces that were maintained at a temperature of 615C in an As4 flux (either in the absence of growth or during molecular beam epitaxy). The reflection high-energy electron diffraction patterns exhibited a 2 x 4 reconstruction, and strong Kikuchi lines which indicated the existence of flat ordered surfaces; regardless of the values of the ion energy or flux density. Cross-sectional transmission electron microscopy showed that sub-surface dislocation loops were generated when the energy was greater than 55eV. The defect density increased with increasing ion energy or flux density. Films which were grown using energies of less than 50eV were free of extended defects. It was concluded that the beneficial effects of ion-assisted molecular beam epitaxy could be achieved without causing ion damage.

J.M.Millunchick, L.Hultman, S.A.Barnett: Journal of Vacuum Science and Technology A, 1995, 13[3], 1155-9