title: Broadband coherent anti-Stokes Raman spectroscopy characterization of polymer thin films.
abstract: Broadband coherent anti-Stokes Raman spectroscopy (CARS) is demonstrated as an effective probe of polymer thin film materials. A simple modification to a 1 kHz broad bandwidth sum frequency generation (SFG) spectrometer permits acquisition of CARS spectra for polymer thin films less than 100 nm thick, a dimension relevant to organic electronic device applications. CARS spectra are compared to the conventional Raman spectra of polystyrene and the resonance-enhanced Raman spectra of poly(3-hexylthiophene). The CARS spectra obtained under these conditions consistently demonstrate enhanced signal-to-noise ratio compared to the spontaneous Raman scattering. The sensitivity of the CARS measurement is limited by the damage threshold of the samples. The dielectic properties of the substrate have a dramatic effect on the detected signal intensity. For ultrathin films, the strongest signals are obtained from fused silica surfaces. Similar to surface-enhanced Raman scattering (SERS), Au also gives a large signal, but contrary to SERS, no surface roughening is necessary.
authors.affiliation: Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8372, USA. zachary.schultz@nist.gov
authors.forename: Zachary D
authors.initials: ZD
authors.lastname: Schultz
authors.forename: Marc C
authors.initials: MC
authors.lastname: Gurau
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Richter
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D008567:Membranes, Artificial; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D008567:Membranes, Artificial; D011108:Polymers