We have used the density functional ab initio method to study the reactivity of small clusters (ammonia reacting with GaAs clusters), and the effects of electric field on adatom-surface interactions (H and Al adsorbed on Si(111) surface). In the case of NH$\sb3$ reactivity at various sites of a Ga$\rm\sb5As\sb5$ cluster, a strong correlation is found between the adsorbate-cluster binding energy and charge transfer. Ionizing the bare cluster to a cationic charge state enables multiple chemisorption of ammonia, which is much less favored on a neutral cluster and can be prohibited on a negatively charged cluster. In the case H and Al adsorbed on a Si(111) surface, the influence of an external electric field, such as that present in a scanning tunnelling microscope (STM), on the chemisorption bond is investigated. The changes in charge distributions, vibrational frequencies and adsorbate desorption barriers are calculated as a function of the strength and direction of the electric field. We find that the characteristics of the chemisorption bond can, to a large extent, be controlled through the externally applied field.
| Identifer | oai:union.ndltd.org:RICE/oai:scholarship.rice.edu:1911/14096 |
| Date | January 1996 |
| Creators | Akpati, Hilary Chukwuma |
| Contributors | Nordlander, Peter |
| Source Sets | Rice University |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | 48 p., application/pdf |
Page generated in 0.002 seconds