AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Tuesday Sessions
       Session NS-TuA

Paper NS-TuA8
Dynamics of Adsorbate Islands with Nanoscale Spacial Resolution: (OH)@sub n@ Formation during the NO/H@sub 2@ Reaction on Pt(001)

Tuesday, October 26, 1999, 4:20 pm, Room 612

Session: Innovative Nanoscale Measurements
Presenter: N. Kruse, Université Libre de Bruxelles, Belgium
Authors: C. Voss, Université Libre de Bruxelles, Belgium
T. Visart de Bocarmé, Université Libre de Bruxelles, Belgium
T. Bär, Université Libre de Bruxelles, Belgium
N. Kruse, Université Libre de Bruxelles, Belgium
Correspondent: Click to Email
Studies by Field Ion Microscopy (FIM) of the catalytic NO hydrogenation (p@sub H2@ = 4 x 10@super -3@ Pa and p@sub NO@ = 3 x 10@super -3@ Pa at 500 K) on the (001) plane of a Pt tip have resulted in the observation of small islands with a size corresponding to 10-30 Pt surface atoms. Simultaneous atom-probe work allowed these islands to be consistently interpreted as being due to the intermediate formation of hydroxyl species in an O@sub ad@/H@sub ad@ coadsorbed layer. Imaging of this reaction phenomenon was achieved by field ionisation of NO at field strengths slightly above those usually present in Scanning Tunneling Microscopy (STM). OH@sub ad@ islands exclusively formed at the layer edge with subsequent movement into the (001) terrace region. Usually one to two islands were observed at the same time with no mergence occurring on collision. Mean lifetimes of several minutes were observed for individual islands before their annihilation at the layer edge. The formation of OH@sub ad@ clusters must be regarded as a collective reaction phenomenon involving a delicate balance of attractive and repulsive forces between adspecies. The results will be presented in a video sequence and compared to a sucessful computer simulation with an automaton lattice model.