title: UV photooxidation and photopatterning of alkanethiolate self-assembled monolayers (SAMs) on GaAs (001).
abstract: We have investigated the photooxidation of alkanethiolate self-assembled monoalyers (SAMs) adsorbed on GaAs (001) using time-of-flight secondary ion mass spectrometry. Both -CH3- and -COOH-terminated SAMs undergo photoreaction to form sulfonated species upon exposure to UV light from a 500 W Hg arc lamp (lambda = 280-440 nm) in the presence of oxygen. In contrast to SAMs adsorbed on metals, the photooxidation of octadecanethiol adsorbed on GaAs can be fit to two first-order reactions: a fast initial reaction followed by a second slower reaction ( approximately 6 times slower). For SAMs with shorter alkyl chain lengths, the photooxidation process is can be fit to a single first-order reaction. Using the optimal photooxidation time, we also demonstrate that SAMs can be successfully UV photopatterned on GaAs substrates producing sharp, well-defined patterns.
authors.affiliation: Department of Chemistry and Center for Materials Innovation, Washington University in St. Louis, Campus Box 1134, One Brooking Drive, St. Louis, Missouri 63130, USA.
authors.forename: Chuanzhen
authors.initials: C
authors.lastname: Zhou
authors.forename: Amy V
authors.initials: AV
authors.lastname: Walker