AVS 46th International Symposium
    Surface Science Division Friday Sessions
       Session SS3+EM-FrM

Paper SS3+EM-FrM4
Kinetics of Abstraction of Monohydride and Dihydride D from Si(100) Surfaces

Friday, October 29, 1999, 9:20 am, Room 604

Session: Reactions on Semiconductors
Presenter: J. Küppers, Universität Bayreuth, Germany
Authors: A. Dinger, Universität Bayreuth, Germany
C. Lutterloh, Universität Bayreuth, Germany
J. Küppers, Universität Bayreuth, Germany
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The interaction of H(D) atoms with Si(100) surfaces and the abstraction of D adsorbed in the monohydride and dihydride phases on Si(100) by H was studied with thermal desorption spectroscopy and direct product rate measurements. H/D atoms were produced in W tube sources heated at 2000 K. H/D atom exposure to clean Si(100) surfaces at 380 K and 640 K lead to the formation of dihydride and monohydride phases with the characteristic desorption peaks at 690 K and 810 K. In addition, after application of high atom fluences, H@sub 2@ (D@sub 2@) peaks were seen at 910 K which are interpreted as a consequence of etching. Etch products were monitored in desorption and during reaction. H atom exposure to monohydride D covered surfaces at 640 K revealed HD and D@sub 2@ as gaseous products. At a saturated monohydride surface about 6% of the adsorbed D occurred in D@sub 2@ products. The kinetics of HD formation is not in accordance with the operation of an Eley-Rideal mechanism. This is most clearly apparent at small D coverages since then the HD rate is constant at decreasing D coverage. Abstraction of D from dihydride phases at 380 K exhibit an Eley-Rideal phenomenology in the HD rates, however a small contribution of D@sub 2@ products (<1%) illustrate that another mechanism also acts in abstraction of D from the dihydride. The results can be explained by the operation of hot-atom mechanisms, in which the probabilities of hot-atom sticking and reaction determine the kinetics of gaseous products formation.