Ion fraction map of He+ scattered from a Si(1 0 0)-(2×1) surface

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: Y1st∼70%, Y2nd∼25%, and Y3rd∼5%. After fitting the experimental charge fraction with the two adjustable parameters v0 (characteristic velocity) and Pc (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 v0=(1.9±0.1)×107 cm/s and Pc=0.34±0.09.