THE ADSORPTION AND BONDING OF CHLORINE AT SILICON(100) INVESTIGATED USING ESD ESDIAD WITH CL+ AND CL- IONS/

The adsorption of chlorine on Si(100) 2x1 surface has been studied usi ng electron stimulated desorption (ESD) and electron stimulated desorp tion ion angular distribution (ESDIAD) in conjunction with AES and gas uptake techniques. ESDIAD and ESD measurements were performed on nega tive as well as positive atomic chlorine species, and the responses wi th the different polarity of charged species are not seen as complemen tary. Gas uptake at the surface proceeds initially with a high stickin g probability with the atomic chlorine resulting from dissociation not being limited to single dimer sites. ESDIAD studies with positive Cl ions reveal normal and off-normal beams associated with symmetric and asymmetric dimers, with relative contributions depending on surface c overage and temperature. Transformations between bonding configuration s seen in positive ion ESDIAD are linked with lateral interactions in the adsorbate layer, and their influence is also evident in the forms of the ion yields of both polarity of species with changing coverage. Negative chlorine ions exhibit a predominance of emission around the s urface normal, and are produced via a dipolar dissociation process. Mi ssing atom defect sites with an associated high electron density are p ostulated as playing a central role in their production. The desorptio n of positive chlorine ions follows mainly from a two-hole, one-electr on (2h1e) repulsive state initiated by the ionisation of the C1 3s lev el.