EXPERIMENTAL-VERIFICATION OF A NEW MECHANISM FOR DISSOCIATIVE CHEMISORPTION - ATOM ABSTRACTION

Abstraction of a F atom from incident F2 by Si(100)- (2×1) is demonstrated by detection of the scattered, complementary F atom. He atom diffraction measurements are consistent with abstraction occurring at dangling bond sites. The low probability for single atom adsorption (P1=0.10±0.01) relative to the total adsorption probability (Pt=0.96±0.02) in the zero coverage limit indicates that the second F atom can also be trapped by the dangling bonds. Both the single and two atom adsorption probabilities decay to zero when the dangling bonds are saturated at 1 ML coverage. Atom abstraction represents a mechanism distinct from the classic one for dissociative chemisorption. © 1995 The American Physical Society.