Reactions of atomic deuterium with C2D5Br on Si(100)

Abstract

The reaction of gas-phase deuterium atoms with C2D5Br (EtBr) adsorbed on Si(100) is studied using temperature programmed desorption and Auger electron spectroscopy. EtBr adsorption on bare Si(100), at 300K, without D atom preexposure, dissociatively chemisorbs into ethyl groups and bromine. Ethyl groups undergo β-deuteride elimination to desorb ethylene at 600K. Bromine is desorbed as the etch product SiBr at 950K. When D atoms are dosed after EtBr, ethylene TPD peaks shift to higher temperature. A small shift (30 to 50K) is attributed to the removal of bromine at low D atom fluences (<6.6×1014atomscm−2). A larger shift (∼100K), with higher D atom fluences, is caused by the adsorption of D onto silicon sites occupied by ethyl groups. The latter prevents β-deuteride elimination until D2 desorption begins. Ethyl groups are removed during exposure to D atoms. The cross sections for ethyl group removal are on the order of 10−17cm2 at temperatures between 300–450K; the relatively low cross sections along with the determined activation energy of 1.12kcalmol−1, suggest ethyl groups are removed through a direct Eley–Rideal mechanism. No evidence is found for the decomposition of ethyl groups during D atom exposure.