Ion fraction map of He + scattered from a Si( [formula omitted])-(2×1) surface

Abstract

Scattering and recoiling imaging spectrometry in the blocking configuration is used to obtain a three-dimensional ion fraction map of 5 keV He + scattered from a Si(1 0 0)-(2×1)-two domain surface. The scattered ion fractions Y are highly sensitive to the alignment of the He + beam with the crystal geometry, with Y varying from a minimum of 2% to a maximum of 10%. Scattering and recoiling imaging code simulations, including Auger-neutralization and charge exchange in the close collision, show that the highest Y values correspond to ions that collide with Si atoms in the outermost surface layers. The experimentally measured fraction of He + surviving as ions from the surface layers are as follows: Y 1st∼70%, Y 2nd∼25%, and Y 3rd∼5%. After fitting the experimental charge fraction with the two adjustable parameters v 0 (characteristic velocity) and P c (charge exchange probability in the close collision) for three blocking exit angles of 35°, 45°, and 55°, good agreement between experiment and simulation was found for v 0=(1.9±0.1)×10 7 cm/s and P c=0.34±0.09.