Fluorine atom abstraction by Si(100) II. Model

Abstract

A model is developed to describe the kinetics of the three scattering channels-unreactive scattering and dissociative chemisorption via single atom abstraction and two atom adsorption-that are present in the interaction of F 2 with Si͑100͒. The model provides a good description of the non-Langmuirian coverage dependence of the probabilities of single atom abstraction and two atom adsorption, yielding insight into the dynamics of the gas-surface interaction. The statistical model is based on the premise that the two dissociative chemisorption channels share a common initial step, F atom abstraction. The subsequent interaction, if any, of the complementary F atom with the surface determines if the overall result is single atom abstraction or two atom adsorption. The results are consistent with the orientation of the incident F 2 molecular axis with respect to the surface affecting the probability of single atom abstraction relative to two atom adsorption. A perpendicular approach favors single atom abstraction because the complementary F atom cannot interact with the surface, whereas a parallel approach allows the F atom to interact with the surface and adsorb. The fate of the complementary F atom is dependent on the occupancy of the site with which it interacts. The model distinguishes between four types of dangling bond sites on the Si͑100͒͑2ϫ1͒ surface, based on the occupancy of the site itself and that of the complementary Si atom in the Si surface dimer. The results show that the unoccupied dangling bond sites on half-filled dimers are about twice as reactive as those on empty dimers, which is consistent with an enhanced reactivity due to a loss of a stabilizing interaction between the two unoccupied dangling bonds on a dimer.

Cl Insertion onSi(100)−(2×1): Etching Under Conditions of Supersaturation

“…5(a). Recent studies of O 2 and F 2 interaction with Si(100) also reported dissociative chemisorption mediated by DBs [12,17,18]. In contrast to Cl 2 , however, the DB merely acts as a catalyst for O 2 dissociation.…”

On the viability of single atom abstraction in the dissociative chemisorption of O2 on the Al(111) surface

“…Note that the model reviewed here is a simplified version of the model discussed in Ref. 35, which pertained to the reaction of F 2 on the Si͑100͒ surface. The simplification arises because all nearest neighbor sites on the Al͑111͒ surface are equivalent, whereas on the Si͑100͒ surface, which undergoes a 2ϫ1 reconstruction, they are not.…”

Dissociation of a Product of a Surface Reaction in the Gas Phase:XeF2Reaction with Si

“…Molecular F 2 has been recently shown to dissociate on Si1002 1 by an atom abstraction mechanism [1][2][3]. This mechanism is distinct from that of classic dissociative chemisorption because a bond of an incident molecule is cleaved upon formation of only a single bond to the surface.…”