Abstraction and desorption kinetics in the reaction of H+D/Si(100) and the relation to surface structure

Kinetics of HD and D-2 desorption from D/Si(100)-2x1 surfaces induced by H atoms has been investigated at temperature range of 97-685 K. Desorption rates of HD and D-2 are measured in real-time by using mass spectrometers during the exposure of D/Si(100) to H atom beam. HD and D-2 rates are not fitted by a hot atom kinetics, but are explained well in terms of adjacent double di-hydrides (DDI)-thermal desorption plus abstraction mechanism. For T(s)greater than or equal to480 K, the pre-adsorbed D atoms are desorbed as D-2 via DDI-desorption (similar to22%), as HD via DDI-desorption (similar to28%), and HD via abstraction (similar to50%). For T(s)less than or equal to310 K, DDI-desorption does not occur, whereas the abstraction proceeds at a constant rate. The yield of DDI-desorption decreases as the surface structure of H/Si(100) changes from 2x1 to 1x1, suggesting the DDI-desorption is associated with a re-formation reaction of a mono-hydride dimer from adjacent two di-hydrides. The activation energy (E-a) for DDI-desorption is similar to0.2 eV. The rate of abstraction does not show Arrhenius-type temperature dependence. The abstraction probability P-HD is estimated at 0.03+/-0.015 (cross section sigma(HD)=0.4+/-0.2 Angstrom(2)) for T(s)less than or equal to310 K. (C) 2002 American Institute of Physics.