An X-Ray Absorption Fine Structure Study of Ordering in Polythiophene Thin Films
Abstract
Thin film organic nonlinear optical (NLO) materials are being investigated for laser hardening applications due to their enhanced processability. Plasma-polymerized thiophene films formed by the flowing afterglow synthesis of polyaromatic heterocycles allow one to modulate the refractive index profile in real-time, thus allowing an organic analog of a rugate to be realized. Since the relationships between the molecular structure, NLO response, and processing conditions are poorly understood, the feasibility of using X-ray Absorption Fine Structure (XAFS) spectroscopy was examined. This method allows the local environment of X-ray absorbing atoms in polythiophene and plasma-polymerized 2,5 dichlorothiophene and 2,5 dibromothiophene thin films at the sulfur (S) K-edge and, as appropriate, the chlorine (Cl) and bromine (Br) K-edges to be probed. Argon absorption was found to limit the data range of the S and Cl edge data. The Br K-edge data indicated that the local Br environment was maintained in the plasma-polymerized films of 2,5 dibromothiophene within experimental error. As a result, XAFS spectroscopy has been shown to be a useful technique for investigating the molecular structure of an important category of nonlinear optical materials.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1993
- Accession Number
- ADA274235
Entities
People
- Guy A. Derose
- H. Jiang
- P. D. Haaland
- T. J. Bunning
- W. W. Adams