Abstract

We present the self-quenching of photoreactions involving the surface system of physisorbed CH₃Br on GaAs(110). Time- of-flight (TOF) measurements of the kinetic energy of CH₃ and Br, and the wavelength dependence, indicate that one channel of photodissociation proceeds by means of dissociative electron attachment (DEA) by thermalized electrons in the GaAs conduction band. The photoreaction rate decreases as the reaction occurs. This phenomenon results from the reduction of the lifetime of photoexcited electrons at the CBM. This reduction in the lifetime is confirmed by photoluminescence measurements. The lifetime decreases because of the production of surface states in the GaAs band gap as the reaction product Br bonds to surface atoms.

© 1993 Optical Society of America