Patricia Thiel

None
Address
320 Spedding Hall
The Ames Laboratory
Ames, IA 50011-3020
Phone 515-294-8985
Email thiel@ameslab.gov

Research Interests

Metal Nanostructures on Semiconductors and Insulators

It is well known that properties of nanoparticles can deviate from properties of the bulk. Not only the size, but also the shape, is important. On surfaces, one striking example of this is the so-called Quantum Size Effect (QSE), which is an electronic stabilization of particular heights of metal particles. This is due to wavelength-matching between the wavelength of electrons semi-confined in the particle, and the height of the particle. The requirement of electron confinement means that this effect is seen most clearly if the metal particle is supported on a poorly-conducting surface. It is not clear whether special electronic properties of nanoparticles can affect chemical reactivity, especially in heterogeneous catalysis. We are studying model systems of metals on semiconductors, and metals on oxides, in order to determine this. An important auxilliary avenue of investigation concerns the kinetics and dynamics that influence particle shape and size in these systems. We are currently investigating silver (an important catalyst in ethylene epoxidation) on Si(111) surfaces. We recently found that the silver islands actually distort in order to maximize the match between the wavelength of electrons confined in the silver islands, and the dimension of the islands.

 

This work is supported by the U.S. Department of Energy, Office of Basic Energy Science, Division of Materials Sciences and Engineering.

 

Surfaces of Complex Metallic Alloys

Surfaces of complex metallic alloys / intermetallics, including quasicrystals, are important because these materials can display anomalous surface properties such as low friction, good oxidation resistance, and low surface energy. Often, however, basic information about these surfaces is lacking. We seek to answer the following questions. Do the surfaces retain the atomic and electronic structure of the bulk—and under what conditions? What are the most active adsorption sites? Can basic surface atomic and electronic structure be related to useful surface properties? How do these materials form interfaces with more conventional ones? Do they serve as templates for nanoparticles in unusual ways? How do they react in oxidizing environments? In the past, we have investigated quasicrystal surfaces extensively. (Quasicrystals are well-ordered, but non-periodic, at the atomic scale. Most of the known phases are Al-rich metallic alloys/intermetallics. They often exhibit a forbidden rotational symmetry, such as the five-fold symmetry element in an icosahedron.) As one example of our findings there, we established unabiguously that the low friction is due–at least in part–to the unusual atomic structure. The expertise that has been established for studying quasicrystals can now be extended to studies of other complex systems, such as Gd-Ge, a prototypical material for magnetic refrigeration.

 

This work is supported by the U.S. Department of Energy, Office of Basic Energy Science, Division of Materials Sciences and Engineering.

 

The following article is a good introduction to quasicrystals:
Thiel, Patricia A. "Quasicrystal Surfaces." Annual Review of Physical Chemistry 59.1 (2008): 129-52.

 

Stability and Coarsening of Metal Nanostructures on Metal Surfaces
We are investigating the ways in which chemical additives destabilize metal nanostructures on metal surfaces. Specifically, the average particle size increases in a process called coarsening, a realization of the old axiom, “The big get bigger." In nanoscale science and technology, that's almost always a bad thing. We are exploring the effect of chemical additives in coarsening of metal islands on metal surfaces, and finding that they can accelerate coarsening rates by as much as three orders of magnitude. We seek a framework of understanding that encompasses different adsorbates, different metals, and different surface crystallographies, with particular emphasis on chalcogens (O, S, Se) as adsorbates and coinage metals (Cu, Ag, Au) as the metals. One effect that is particularly interesting is the formation of adsorbate-metal complexes that can be efficient carriers of mass between metal nanoparticles.

 

This work is supported by the National Science Foundation.


        Project Affiliations:

        Group Website:
        Thiel Research Goup
        
        

(Chronologically most recent on top)Education

  • Postdoctoral Research Universität München (with Gerhard Ertl), 1981
  • Ph.D. Chemistry, California Institute of Technology, Pasadena, CA (with W.H. Weinberg), 1981
  • B. A. Chemistry (summa cum laude) Macalester College, St. Paul, MN, 1975

(Chronologically most recent on top)Professional Appointments

  • 2008 - 2009 Division Director for Science and Technology (aka Chief Research Officer) of Ames Laboratory
  • 1999 - 2002 Chair, Dept. of Chemistry, Iowa State University
  • 1988 - 2003 Program Director, Materials Chemistry, Ames Laboratory
  • 1983 - present Professor (Assistant-Associate-Full-Distinguished), Dept. of Chemistry, Iowa State University
  • 1983 - present Chemist (Associate-Full-Senior), Ames Laboratory
  • 1982 - 1983 Technical Staff Member, Sandia National Laboratories, Livermore, CA
  • 1981 Postdoctoral Research, Universität München, Germany
  • 1974 - 1976 Scientist, Research Division of Control Data Corp., Minneapolis, MN

(Chronologically most recent on top)Honors & Awards

  • 2010 David Adler Lectureship Award of the American Physical Society
  • 2010 Arthur W. Adamson Award of the American Chemical Society, for Distinguished Service in the Advancement of Surface Chemistry
  • 2008 National Honorary Member of Iota Sigma Pi
  • 2005 Dr. Honoris Causa (honorary degree) from the Institut National Polytechnic de Lorraine
  • 2004 Fellow of the Institute of Physics
  • 2002 Distinguished Professor of Iowa State University
  • 2001 Fellow of the American Vacuum Society
  • 2001 American Physical Society
  • 2001 Invitation Fellow of the JSPS (Japan Society for the Promotion of Science)
  • 1998 Department of Energy Award for Outstanding Scientific Accomplishment in Materials Chemistry (team)
  • 1998 Iowa State University Foundation Award for Outstanding Achievement in Research
  • 1996 Wilkinson Teaching Award (ISU-Dept. of Chemistry)
  • 1991 - 1996 Faculty Award for Women in Science and Engineering (NSF)
  • 1986 - 1990 Camille and Henry Dreyfus Teacher-Scholar
  • 1985 - 1989 National Science Foundation Presidential Young Investigator
  • 1984 - 1986 Alfred P. Sloan Foundation Fellowship
  • 1980 Herbert Newby McCoy Award for Outstanding Graduate Research: Caltech
  • 1980 Electrochemical Society (Southern California--Nevada Section) Graduate Student Award
  • 1979 - 1980 IBM Predoctoral Fellowship
  • 1979 - 1980 American Vacuum Society Scholarship
  • 1976 - 1979 National Science Foundation Predoctoral Fellowship
  • 1971 - 1975 National Merit Scholarship
  • National Honorary Societies: Phi Beta Kappa, Phi Lambda Upsilon, Pi Mu Epsilon

(Chronologically most recent on top)Publications with the Ames Laboratory

2011
Belianinov A; Unal B; Ho K M; Wang C Z; Evans J W; Tringides M C; Thiel P A . 2011. Nucleation and growth of Ag islands on the (root 3 x root 3)R30 degrees phase of Ag on Si(111). Journal of Physics-Condensed Matter. 23:265002. abstract
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Yuen C D; Unal B; Jing D P; Thiel P A . 2011. Weak bonding of Zn in an Al-based approximant based on surface measurements. Philosophical Magazine. 91:2879-2888. abstract
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Russell S M; Shen M M; Liu D J; Thiel P A . 2011. Adsorption of sulfur on Ag(100). Surface Science. 605:520-527. abstract
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Shen M M; Jenks C J; Evans J W; Thiel P A . 2011. How Sulfur Controls Nucleation of Ag Islands on Ag(111). Topics in Catalysis. 54:83-89. abstract
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Duguet T; Unal B; Ledieu J; Dubois J M; Fournee V; Thiel P A . 2011. Nanodomains due to Phason Defects at a Quasicrystal Surface. Physical Review Letters. 106:076101. abstract
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Duguet T; Han Y; Yuen C; Jing D P; Unal B; Evans J W; Thiel P A . 2011. Self-assembly of metal nanostructures on binary alloy surfaces. Proceedings of the National Academy of Sciences of the United States of America. 108:989-994. abstract
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2010
Belianinov A; Unal B; Lu N; Ji M; Ho K M; Wang C Z; Tringides M C; Thiel P A . 2010. Islands and holes as measures of mass balance in growth of the (root 3x root 3)R30 degrees phase of Ag on Si(111). Physical Review B. 82:245413. abstract
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Duguet T; Unal B; Han Y; Evans J W; Ledieu J; Jenks C J; Dubois J M; Fournee V; Thiel P A . 2010. Variation of growth morphology with chemical composition of terraces: Ag on a twofold surface of a decagonal Al-Cu-Co quasicrystal. Physical Review B. 82:224204. abstract
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Thiel P A; Shen M M; Liu D J; Evans J W . 2010. Adsorbate-enhanced transport of metals on metal surfaces: Oxygen and sulfur on coinage metals. Journal of Vacuum Science & Technology A. 28:1285-1298. abstract
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Evans J W; Thiel P A . 2010. A Little Chemistry Helps the Big Get Bigger. Science. 330:599-600. abstract
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