Surface Structure Analysis by Low Energy Ne exp + and H sub 2 O exp + Scattering

摘要

The experimental procedures described in this thesis make it possible to separate the effects of neutralisation from shadowing processes. According to this method the angular distributions of scattered 4 keV Ne exp + ions are compared with similar distributions of O exp - ions. These O exp - ions originate from 4 keV H sub 2 O exp + molecules which are dissociatively scattered. The charge-exchange processes which lead to the production of O exp - ions are found to depend on the scattering parameters in a way similar to the neutralisation processes of Ne exp + . The opposite influences of these processes on the scattering intensities cause differences in the angular distributions of Ne exp + and O exp - ions. The non-zero intensity of scattered ions for directions where a zero intensity is expected due to shadowing (i.e. in close-packed crystallographic directions: is attributed to scattering from defects and irregularities in the surface. The author used this intensity to monitor the bombardment-induced damage of the surface. The effects of shadowing are investigated in the case where the second layer also contributes to the intensity of scattered ions. For the interpretation the shadow cone mode is again used, but this time distortions of the shadow by other target atoms have been taken into account. For certain directions of incidence of the primary beam it was found that target atoms in the first layer focus the impinging ions on the atoms of the second layer. The methods described are applied to investigate the structure of the oxygen-covered Cu(110: surface. (Atomindex citation 12:611625)