Research is performed to develop and extend optical tools for the characterization of thin films, surfaces, and buried interfaces. Both linear spectroscopies (spectroscopic ellipsometry, Fourier-transform infrared absorption, Raman scattering) and nonlinear spectroscopies (vibrationally resonant sum frequency generation, SFG, coherent anti-Stokes Raman scattering, CARS, time-resolved absorption spectroscopy, TAS, and 2D correlation spectroscopy) are explored. Emphasis is placed on the use of optical cavities and evanescent fields to provide selectivity and the use of broad-bandwidth, ultrafast lasers to improve sensitivity. Interfaces of interest include those important to the emerging technologies of molecular electronics, organic electronics, photovoltaics (both organic, OPV, and inorganic), and biomembrane based biosensors. Recent work includes characterization of the incorporation of small molecules and proteins into self-assembled organic layers, the study of additives used in electrodeposition of semiconductor device interconnects, organic electronic thin films, the study of the buried polymer/dielectric interface in organic thin-film transistors, organic electrochemical transistors, and model studies of polymer/fullerene interfaces in OPV devices.
Research is also conducted on extension of optical spectroscopies to the characterization of transient states through field modulation and pump-probe techniques, and to the characterization of localized states through microscopy and photomodulated scanned probes.
For all relevant techniques, the emphasis is on studies closely tied to functioning devices: in-situ studies of active layer formation and in-operando spectroscopy of complete devices.
Biomembranes; Electrochemistry; Interfaces; Molecular electronics; Nonlinear microscopy; Nonlinear optics; Organic electronics; Photomodulated; Photovoltaics; Polymers; Scanned probes; Surface chemistry;