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Jason
F. Weaver
Associate Professor
Ph.D., 1998, Stanford
University
Gas-surface Reactivity and Dynamics
Atomic and Molecular Beam Methods
Surface Spectroscopy
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Brief Description
of Current Research
Our research focuses on advancing the molecular-level understanding of
chemical reactions occurring on solid surfaces. Such reactions are
fundamental to heterogeneous catalysis and semiconductor processing, yet
remain poorly understood at the molecular level. My students and I
investigate surface chemical reactions experimentally using sensitive
surface spectroscopic techniques combined with reactive beam scattering
in ultrahigh vacuum (UHV). This is a powerful approach for probing the
mechanistic details of surface reactions as it enables one to prepare
atomically clean surfaces and to induce chemical reactions on these
surfaces in a highly controlled manner. The combined use of reactive
beam scattering and surface analysis also provides comprehensive
information about surface chemical reactions since both the gaseous and
surface reaction products are analyzed with high resolution. We also
use in situ scanning tunneling microscopy (STM) to obtain
real-space images of atoms on solid surfaces. Investigations with STM
enable us to examine how different, local arrangements of atoms
influence the reactivity of a solid surface, and, conversely, how
chemical reactions modify surface structures over nanometer dimensions.
Radical-Surface Reactions
Current work is aimed at elucidating the mechanisms and kinetics of reactions
induced by the collisions of gas-phase radicals, particularly oxygen atoms, at
solid surfaces. This class of surface chemical reactions is central to
technological applications that occur in extreme environments, such as in flames
and plasmas, and is very interesting from a scientific viewpoint. The
collisions of gas-phase radicals at a solid surface can stimulate a variety of
chemical phenomena that occur by so-called non-thermal mechanisms, which means
that reactions occur without the reactants thermally equilibrating to the
surface. We use beam scattering methods to investigate the surface reactions of
gaseous radicals, and we have also been using quantum chemical simulations to
complement our experimental efforts. Our interest includes developing an
understanding of how reaction conditions and surface properties influence the
kinetics of radical-surface reactions so that predictive models of
radical-surface chemistry can ultimately be developed.
Reactivity of Model Catalysts
We are also investigating the oxidation and reactivity of model noble-metal
catalysts. The basic goal of this work is to utilize highly reactive atomic
oxygen beams to oxidize metallic single crystals and nanoclusters in a UHV
chamber so that the surface oxygen phases that exist on metal catalysts under
industrially relevant conditions (i.e. atmospheric pressure) can be
prepared and characterized in the well-controlled ultrahigh vacuum environment.
Using this approach, we hope to gain insights for understanding the reactivity
of high-concentration oxygen phases that are important in many applications of
catalysis. In addition, a key question that we seek to address is how and why
the chemical reactivity of metallic nanoclusters is influenced by the
size-dependent geometric and electronic structure of the clusters. This is
crucial to the successful molecular design of new catalysts for use in
applications ranging from pollution control and energy conversion to the
production of fine chemicals.
Selected Publications
- "Oxidation of Pt(100)-hex-R0.7º by Gas-Phase Oxygen Atoms", R.B.
Shumbera, H.H. Kan and J.F. Weaver, Surf. Sci. (to appear,
2006) .
- "Adsorption of Gas-Phase Oxygen Atoms on Pt(100)-hex-R0.7º: Evidence
of a Metastable Chemisorbed Phase", R.B. Shumbera, H.H. Kan and J.F.
Weaver, Surf. Sci. 600 (2006) 2928-2937.
- “Kinetics of CO Oxidation on High-Concentration Phases of Atomic
Oxygen on Pt(111)”, A.L. Gerrard and J.F. Weaver, J. Chem. Phys.
123 (2005) 224703:1-17.
- “Oxidation of Pt(111) by Gas-Phase Oxygen Atoms”, J.F.Weaver, J.-J.
Chen and A.L. Gerrard, Surf. Sci. 592 (2005) 83-103.
- “A Density Functional Theory Study of Atomic Nitrogen Abstraction
from Si(100)-(2x1) by a Gaseous O(3P) Atom”, P.E.
Herrera-Morales and J.F. Weaver, J. Chem. Phys.
122 (2005) 234705:1-10.
- “Oxidation of Nitrided Si(100) by Gaseous Atomic and Molecular
Oxygen”, A.L. Gerrard, J.-J. Chen and J.F. Weaver, J. Phys. Chem. B.,
Vol. 109, 8017-8028 (2005).
- “Electron energy loss spectroscopic investigation of Ni metal and
NiO before and after surface reduction by Ar+ bombardment”,
H.A.E. Hagelin-Weaver, J.F. Weaver, G.B. Hoflund and G.N. Salaita, J.
Elect. Spectros. Rel. Phenom., Vol. 134, 139-171 (2004).
- “Adsorption and reaction of low molecular weight alkanes on metallic
single crystal surfaces”, J.F. Weaver, A.F. Carlsson and R.J. Madix,
Surf. Sci. Rep., Vol. 50, 107-199 (2003).
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