Sabrina J. Diol

CURRICULUM VITAE

Center for Photoinduced Charge Transfer
Department of Physics
University of Rochester
Rochester, NY 14627-0216
Tel: (716) 275-0405
Fax: (716) 242-9485
email: sabrina@pas.rochester.edu

Research

I am primarily working on picosecond and femtosecond electron dynamics at GaAs (100) surfaces and interfaces (GaAs/electrolyte). As a member of the Ultra High Vacuum Group at the NSF Center for Photoinduced Charge transfer, I am also investigating similar dynamics in other materials e.g. SnS2, AgX (silver halides), and polymers.

The research of carrier dynamics at surfaces and interfaces is driven by a host of technological applications. There have been proposals to utilize hot electrons at the semiconductor-liquid interface in solar cells to double the theoretical maximum energy conversion efficiencies. The issue is whether or not hot electrons from the semiconductor can be stored through electron transfer to discrete molecular states i.e. can interfacial charge transfer processes occur competitively with thermalization dynamics in the solid state? Investigation of this interface also serves as a model for charge transfer at electrodes. More fundamentally, we are also interested in the charge transfer process at such a hybrid juntion: Can electron transfer at such a hybrid junction occur in the adiabatic regime?

At the Center, we have performed surface sensitive time resolved two photon photoemission measurements of electron relaxation at MBE grown GaAs (100) surface quantum wells in which the electron distribution is directly determined with 0.1-0.2 eV resolution. The relaxation dynamics were studied in the 1 eV excess energy range corresponding to the relevant energetics for surface photochemistry. The electron lifetime spans 50 fs to 600 fs depending on QW doping, QW thickness and excitation density. Electron transfer to outer-sphere acceptors (ferricenium) has also been probed in situ where the electron lifetime at a semiconductor/electrolyte interface is measured using time correlated single photon counting. From the concentration dependence and other studies, the molecular acceptors appear to have electron capture cross-sections comparable to molecular cross-sections. This is the optimal condition for hot electron capture. These results also indicate that for suitable acceptor concentrations at the surface, the electron transfer can occur on timescales (1 ps) of the same order as electron relaxation. Such fast electron transfer is also characteristic of the adiabatic regime. These combined studies provide parameters to make the hot electron transfer channel competitive with electron relaxation enabling a future generation of solar cells exploiting hot electrons.

Publications

  1. S. J. Diol, C. C. Miller, C. A. Schmuttenmaer, J. Cao, Y. Gao, D. A. Mantell, and R. J. D. Miller, Photogenerated Hot Electron Dynamics at GaAs (100) Surfaces, Journal of Physics D, submitted July 1996
  2. C. C. Miller, S. J. Diol, C. A. Schmuttenmaer, J. Cao, D. A. Mantell, R. J. D. Miller, and Y. Gao, Reverse Surface Photovoltaic Effects in GaAs Surface Quantum Wells, Journal of Physics D, submitted July 1996
  3. S. Xu, C. C. Miller, S. J. Diol, Y. Gao, D. A. Mantell, M. G. Mason, A. A. Muenter, B. A. Parkinson, and R. J. D. Miller, Ultrafast Electron Dynamics in Two Dimensional Layered Systems: Two-Photon Photoemission Studies of SnS2, Chemical Physics Letters, submitted October 1996
  4. S. J. Diol and R. J. D. Miller, Ultrafast Studies of Imaging Processes, Journal of Imaging Science and Technology, submitted August 1996
  5. S. J. Diol, C. C. Miller, Y. Gao, and R. J. D. Miller, Hot Electron Reaction Dynamics at GaAs (100) Surface Quantum Wells, Ultrafast Phenomena Conference Proceedings 1996, in print
  6. S. J. Diol, Electron Dynamics at GaAs (100) Surfaces and Interfaces: Probing Issues Behind the Hot Electron Model, Link Research Reports 1996, in print
  7. S. J. Diol, C. Miller, Y. Gao, and R. J. D. Miller, Femtosecond Hot Electron Relaxation Processes and Hot Electron Reaction Dynamics at GaAs Surfaces, Conference on Electro-Optics/Quantum Electronics and Laser Science, postdeadline paper QPD21, 1995
  8. Sabrina Diol, Materials Research Society Bulletin, Material World 95 Brings Science to School Children, 21, Iss. 3, 95 (1996)
  9. Sabrina Diol and Eileen Korenic, Materials Research Society Bulletin, Promote Science with the Science Demonstrations Handbook, 21, Iss. 10 (1996)

Professional Activity