IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Tuesday Sessions
       Session SS+BI-TuA

Paper SS+BI-TuA3
Adsorption and Photoinitiated Chemistry on Organic-functionalized Semiconductor Surfaces

Tuesday, October 30, 2001, 2:40 pm, Room 120

Session: Poirier Memorial Session: Self-Assembled Monolayers II
Presenter: N. Camillone III, Columbia University
Authors: N. Camillone III, Columbia University
K. Adib, Columbia University
R.M. Osgood, Jr., Columbia University
Correspondent: Click to Email
Greg Poirier's pioneering imaging work had a specific and important role in the scientific and intellectual development of one of the authors (N.C.), and played an instrumental part in the growth of our understanding of the structure and dynamics of self-assembled monolayers. Many experiments have been conceived based upon this understanding. We report results of one such experiment, which characterizes the growth and photoinitiated chemistry of methyl bromide monolayers adsorbed at the surface of short-chain thiolate monolayers on GaAs(110) surfaces. The thiolate monolayers are grown in UHV by exposure of the GaAs to alkyl disulfides. Temperature programmed desorption reveals that the CH@sub 3@Br-surface interactions are strongly modified by the presence of the thiolate spacer layer. With increasing chain length, the CH@sub 3@Br becomes progressively less tightly-bound. The simple layer-by-layer growth behavior observed on bare GaAs(110) is lost, and CH@sub 3@Br appears to form clusters at critical coverages. Exposure to 248 nm light results in the dissociation of the CH@sub 3@Br, most likely due to the dissociative attachment of excited substrate electrons. The cross section for the reaction is strongly enhanced in the case of the ethyl disulfide spacer layer. The implications of the results will be discussed within the context of electron transport through molecular spacers, adsorbate affinity level shifts, and deexcitation mechanisms.