The Faculty

Focus

Molecular structure and dynamics using scanning tunneling and atomic force microscopy

Biography

Born Brooklyn, New York, 1954.
University of Rochester, B.A., S.B., 1975.
University of California, Berkeley, M.S., 1977; Ph.D., 1979.
Bell Laboratories Postdoctoral Research Fellow, 1979-80.
The University of Chicago, Professor, 1980-.
Director, The James Franck Institute, 2001-2007.
Director, MURI Center for Materials Chemistry in the Space Environment, 2001-.
Director, University of Chicago Materials Research Science and Engineering Center (MRSEC), 1997-2001.

Accolades

Visiting Fellow, JILA.
Fellow, American Physical Society.
Fellow, American Association for the Advancement of Science, 2006-.
1996 Chairman, Division of Chemical Physics, American Physical Society.
1992-1993 Visiting Fellow, Joint Institute for Laboratory Astrophysics, Univ. of Colorado, Boulder.
1988 Marlow Medal of the Faraday Division of the Royal Society of Chemistry.
1984-1986 IBM Faculty Development Award.
1983-1987 Alfred P. Sloan Fellow.
1980 Camille and Henry Dreyfus Young Faculty in Chemistry Award.

Research Interests

Our research interests currently center on using experimental and theoretical techniques to address fundamental questions in the fields of surface chemistry and catalysis, surface physics, and materials research, and, most recently, thin film polymer dynamics and AFM imaging studies of bacterial cell wall structure. In particular, we are using a variety of molecular beam, laser spectroscopic, and scanning probe microscopy techniques, as well as computational tools such as molecular dynamics, to examine issues central to our understanding of surface chemical dynamics. Illustrative topics include: surface chemical kinetics and reaction dynamics, surface photochemistry, metallic oxidation and corrosion, atomically structured thin films, supersonic beam growth of electronic materials, and, most recently, thin film polymer dynamics. These studies are being conducted under ultra-high vacuum conditions, with recent extension to electrochemical environments. They are motivated by a desire to understand and control surface chemical processes at the molecular level, and by the increasing need to understand the physical properties of low-dimensional interfacial systems.

Scattering measurements form the basis for one part of our program, encompass-ing elastic, inelastic, and reactive scattering, as well as laser-surface interactions. These measurements are complemented by real-space imaging techniques such as scanning tunneling and atomic force microscopies, as well as more conventional SEM imaging. Structural measurements utilizing elastic helium diffraction provide valuable information on surface charge density distributions, gas-surface interaction potentials, overlayer structure, surface ordering kinetics, and two-dimensional phase transitions. Inelastic scattering measurements examine the energy exchange processes that occur during gas-surface collisions. In one class of studies, quantum state selected beams are being used to study collision-induced energy transfer. Another class of inelastic scattering experiments focuses on surface phonon spectroscopy. These measurements are a 2D analog of inelastic neutron scattering, and are allowing us to study the surface vibrational properties of clean and adsorbate covered surfaces. Recent helium and electron scattering experiments have examined the dynamical behavior of smooth, stepped, and alloyed surfaces, revealing important differences between these systems and the behavior of bulk matter.

Figure 1

Figure 2

Reactive scattering studies are also in progress. Here we are examining the potential energy surfaces which govern important heterogeneous processes such as combustion, catalysis and interface corrosion. We are currently utilizing very powerful and general multiple-modulated-beam scattering methodologies developed in our group to decompose complex heterogeneous reaction mechanisms into their constituent elementary reaction steps. Our newest endeavor in this area is to grow semiconducting materials using supersonic beam epitaxy. Such beam growth experiments permit materials synthesis to occur under kinetic rather than thermodynamic control, allowing for the production of fascinating new metastable materials. Finally, experiments dealing with either electron-stimulated or optically-driven surface chemical processes are also underway. These studies include synergistic effects in metallic oxidation/corrosion, as well as photodesorption induced by resonant laser excitation. Experiments conducted in our group have shown that both thermal and non-thermal (photo-chemical) processes can occur during UV-laser induced desorption. These results suggest that a variety of photochemical pathways may be found at surfaces with time-scales that compete with energy randomization.Reactive scattering studies now include the interaction of supersonic and hyperthermal beams of atomic oxygen with metallic, inorganic, and polymeric interfaces, adding to our knowledge of fundamental surface chemistry in extreme environments. These latter studies are part of a large effort in understanding the stability and reactivity of materials placed in the space environment.

Most recently, we have launched a major effort utilizing time-lapse atomic force microscopy to non-destructively monitor thin film polymer dynamics. We have tracked the temporal evolution of individual defects in polymer thin films, observing phase separation mechanisms and microdomain movement which are influenced by the chemical and physical characteristics of the underlying substrate. This work has now been extended to encompass polymer self-organization under nanoscale spatial confinement. Related projects involving self-assembled monolayers are underway. These projects will hopefully lead to novel electronic, magnetic, and optical materials. Encouraged by the success of imaging these ÒsoftÓ and complex systems, we have also embarked on exploratory projects involving biological materials in which AFM is being used to image, for example, genetically related drug-susceptible and drug-resistant bacteria.

Figure 3

Selected References

1.  Structural and topological differences between a glycopeptide-intermediate resistant clinical strain and vancomycin-susceptible strains of Staphylococcus aureus revealed by atomic force  microscopy, Susan Boyle-Vavra, Jongin Hahm, S. J. Sibener, and Robert S. Daum, Antimicrobial Agents and Chemotherapy, 44, 3456-3460 (2000). PMC90224

2.  Hierarchical Assembly and Compliance of Aligned Nanoscale Polymer Cylinders in Confinement, D. Sundrani, S.B. Darling, and S.J. Sibener, Langmuir 20, 5091-5099 (2004).

3.  Atomic scattering as a probe of polymer surface and thin film dynamics Freedman, M. A., Rosenbaum, A. W. & Sibener, S. J., Physical Review B, 2007, 75(11).

4.  Photochemical Study of the Transport Properties of Gases in Polymer Films, A. L. Cisse, E. Grossman, and S. J. Sibener, J. Phys. Chem. B, 112, 7166-7170 (2008).

5.  In-Situ High-Temperature Studies of Diblock Copolymer Structural Evolution, Nataliya A. Yufa, Jason Li, and S. J. Sibener, Macromolecules 42, 2667-2671 (2009).

6.  Comparative Surface Dynamics of Amorphous and Semicrystalline Polymer Films, James S. Becker, Ryan D. Brown, Daniel R. Killelea, Hanqiu Yuan, and S. J. Sibener, Proceedings of the National Academy of Sciences, PNAS 108, 977-982 (2011). PMC3024667

7.  Interfacial Chemistry of Poly(methyl methacrylate) Arising from Exposure to Vacuum-Ultraviolet Light and Atomic Oxygen, Hanqiu Yuan, Daniel R. Killelea, Sanja Tepavcevic, Scott I. Kelber, and S. J. Sibener, J. Phys. Chem. A 115, 3736-3745 (2011).

8.  Determination of the Sticking Coefficient and Scattering Dynamics of Water on Ice Using Molecular Beam Techniques, K. D. Gibson, Daniel R. Killelea, Hanqiu Yuan, James S. Becker and S. J. Sibener, J. Chem. Phys. 134, 034703/1-7 (2011).

9.  Chiral Domains Achieved by Surface Adsorption of Achiral Nickel Tetraphenyl- or Octaethylporphyrin on Smooth and Locally Kinked Au(111), Lieve G. Teugels, L. Gaby     Avila-Bront, and S.J. Sibener, J. Phys. Chem. C  115, 2826-2834 (2011).

10.  Rough Waters (First Place, AAAS Science/NSF International Science & Engineering Visualization Challenge – Photography Category), Seth B. Darling and Steven J. Sibener, Science (Cover Article) 331, 852 (2011).

11. Scattering of High-Incident-Energy Kr and Xe from Ice:  Evidence That a Major Channel Involves Penetration into the Bulk, K. D. Gibson, Daniel R. Killelea, Hanqiu Yuan, James S. Becker, Subha Pratihar, Paranjothy Manikandan, Swapnil C., Kohale, W. L. Hase, S. J. Sibener, J. Phys. Chem. C, 116, 14264-14273 (2012).

12. Structural Investigations of the (5 x √3) Striped Phase of Annealed 11-Phenoxy Undecanethiol Self-Assembled Monolayers on Au(111), Miki Nakayama, Natalie A. Kautz, Tuo Wang, Hanqiu Yuan, S. J. Sibener, J. Phys. Chem. C 116, 6298-6306 (2012).

13.  Dynamics of Molecular and Polymeric Interfaces Probed with Atomic Beam Scattering and Scanning Probe Imaging, Ryan D. Brown, Qianqian Tong, James S. Becker, Miriam A. Freedman, Nataliya A. Yufa, and S. J. Sibener, Faraday Discussion 157 on Molecular Reaction Dynamics in Gases, Liquids, and Interfaces, Faraday Discuss. 157, 307-323 (2012).

14.  Alignment of Benzene Thin Films on Self-Assembled Monolayers by Surface Templating, Hanqiu Yuan, K. D. Gibson, Daniel R. Killelea, and S. J. Sibener, Surface Sci. 609, 177-182 (2013).

15.  The Hybridization of Surface Waves with Organic Adlayer Librations:  A Helium Atom Scattering and Density Functional Perturbation Theory Study of Methyl-Si(111), Ryan D. Brown, Zachary M. Hund, Davide Campi, Leslie E. O’Leary, Nathan S. Lewis, M. Bernasconi, G. Benedek,  and S. J. Sibener, Physical Review Letters 110, 156102/1-5 (2013).