AVS 49th International Symposium
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA7
Surface Nanostructuring to Control Size and Composition of Individual Oxide Supported Nanoparticles

Monday, November 4, 2002, 4:00 pm, Room C-110

Session: Nucleation & Growth of Metals on Oxides & Semiconductors
Presenter: A. Kolmakov, University of California, Santa Barbara
Authors: A. Kolmakov, University of California, Santa Barbara
D.W. Goodman, Texas A&M University
Correspondent: Click to Email
A key to the technological utilization of oxide supported metal nanoparticles as an active element in gas sensing devices and catalysts is an atomic level understanding of their role in the chemical reaction. The chemical and physical properties of nanoparticles dispersed on oxide surfaces exhibit a marked dependency on their size, shape, composition and electronic interaction with the support. To explore this avenue a umber of methods of producing and delivery of size selected clusters from the gas or liquid phase to the oxide surfaces have been developed during the last decade. Alternatively, recent achievements in single molecule and clusters spectroscopy with NSOM and SPM and TEM proved the feasibility of so called individual approach where instead of probing the ensemble of size selected particles, imaging and spectroscopy of the individual oxide supported nanoparticles with different sizes and composition is performed and compared during the single experiment. Using Ag, Au and alloy clusters supported on TiO@sub2@ (110) as a model system, we demonstrate several experimental schemes for studying individual supported metal clusters using oxide surface nanostructuring in conjunction with SPM. Namely, on slightly reduced TiO@sub2@ we create laterally confined and precisely located areas with controllably modulated defect densities by exploiting a "tip shadowing" technique to synthesize a nanostructured mask. Since the diffusion length of the adsorbate atoms and eventually the cluster nucleation density are strongly mediated by surface defect densities in these areas, a well-defined and controllable variety of cluster sizes is accessible for imaging and spectroscopy within the field of view of the SPM. A similar procedure is applied for tuning the doping level of individual, metal particles. The spectroscopic and morphological changes of the individual clusters were probed in situ while exposuring the sample to elevated pressure of reactive gases.