David P. Pullman
Associate Professor
Physical Chemistry
Undergraduate Adviser
Office: CSL 301
Office Phone: 619-594-5573
e-mail: dpullman_at_sciences.sdsu.edu
Research Interests
The emphasis of our research is on unraveling the mechanisms by which molecules react on solid surfaces. Such reactions play a critical role in a variety of naturally occurring and technologically important processes, including the fabrication of modern electronic devices, heterogeneous catalysis, and corrosion. The viewpoint we take is that control and optimization of these surface reactions is best accomplished if details of the reactions are understood on a molecular scale.
Examples of ongoing projects:
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Fundamental Studies of Nonthermal Means of Removing Ligands from Technologically Important
Surfaces.
With the diminishing size of microelectronic chips, growing the films that compose the circuits at low temperature is increasingly advantageous in order to minimize interdiffusion of atoms at heterojunctions. In chemical vapor deposition, which is one of the chief methods for growing thin films of various materials, high substrate temperatures have traditionally been employed to overcome activation barriers that limit the film growth rate. These barriers normally are associated either with the dissociative adsorption of a precursor molecule or with the desorption of a surface-bound ligand that blocks sites needed for further adsorption of precursors. Our efforts currently focus on collisionally activating the desorption of ligands with high-energy rare-gas atoms produced in supersonic beams. -
Dynamics of Recombinative Desorption of H2 from Si(100).
The chemistry of hydrogen on the Si(100) surface has become a basic model for understanding the principles of reactivity between gas phase molecules and covalent surfaces. Remarkably, the mechanism of dissociative adsorption of H2 on Si(100) and of the reciprocal process, recombinative desorption of H2, remains unclear and controversial. The goal of our current studies is to determine the structure of the transition state for desorption and thus provide a key element to understanding the mechanism of desorption/adsorption. - Optimizing the Growth of Gold Thin Films Under Highly Controlled Conditions.
This project was designed specifically for undergraduates. The scientific goal is to elucidate the mechanism by which gold grains coalesce to form larger, well-ordered grains. In particular, we are examining whether there is a correlation between the coalescence and the removal of carbon contaminants (via oxidation) from the gold grains. The educational goals are to introduce the students to surface science, thin film growth, scanning tunneling microscopy, and vacuum technology.
To carry out our work, we utilize sensitive ultrahigh vacuum surface analytical techniques, including molecular beam scattering, thermal desorption spectroscopy, Auger spectroscopy, and scanning tunneling spectroscopy. A schematic diagram of one of our molecular beam scattering machines is shown in the figure below.
In the course of their research, students in the group learn not only the underlying surface chemistry involved in their projects but also data analysis techniques, data acquisition techniques, vacuum technology, computer modeling and programming, and the design and construction of electronic circuits.
Selected Publications
- Karen I. Peterson, David Pullman, Wei Lin, Andrea J. Minei, and Stewart E. Novick, "Microwave spectra and ab initio studies of Ar-propane and Ne-propane complexes: Structure and dynamics," J. Chem. Phys. (in press, October 2007).
- C.D. Zeinalipour-Yazdi and D.P. Pullman, "Correlation of Polarizabilities with Van Der Waals Interactions in pi-Systems," J. Phys. Chem. B 110, 24260-24265 (2006).
- D.P. Pullman and K.I. Peterson, "Investigating Intermolecular Interactions via Scanning Tunneling Microscopy: An Experiment for the Physical Chemistry Laboratory," J. Chem. Ed., 81, 549-552 (2004).
- D.P. Pullman, A.A. Tsekouras, Y.L. Li, J.J. Yang, M.R. Tate, D. Gosalvez-Blanco, K.B. Laughlin, M.T. Schulberg, and S.T. Ceyer, "Reactivity of Fluorinated Si(100)," J. Phys. Chem. B, 105, 486-496 (2001).
- Steven Chambreau, Monica L. Neuburger, Tom Ho, Brian Funk, and David Pullman, Low Cost, Mechanically Refrigerated Diffusion Pump Baffle for Ultrahigh Vacuum Chambers," J. Vac. Sci. Technol. A., 18, 2581-2585 (2000).
- M.L. Neuburger and D.P. Pullman, "On the Viability of Atom Abstraction in the Dissociative Chemisorption of O2 On the Al(111) Surface," J. Chem. Phys., 113, 1249-1257 (2000).
- M.R. Tate, D.P. Pullman, Y.L. Li, D. Gosalvez-Blanco, A.A. Tsekouras, and S.T. Ceyer, "Fluorine Atom Abstraction by Si(100) II. Model," J. Chem. Phys., 112, 5190-5204 (2000).