Changes in Electron-Phonon Coupling Across a Bulk Phase Transition in Copolymer Films of Vinylidene Fluoride (70%) with Trifluoroethylene (30%)

Authors

C. N. Borca, University of Nebraska-Lincoln
Shireen Adenwalla, University of Nebraska-LincolnFollow
Jaewu Choi, Louisiana State University, Baton RougeFollow
Lee Robertson, Oak Ridge National Laboratory
H. You, Argonne National Laboratory, Argonne, IL
V. M. Fridkin, 1nst. Crystallography, Russian Academy of Sciences, 59 Leninsky Prospekt, 11 7333 Moscow, Russia
S. P. Palto, 1nst. Crystallography, Russian Academy of Sciences, 59 Leninsky Prospekt, 11 7333 Moscow, Russia
N. Petukhova, 1nst. Crystallography, Russian Academy of Sciences, 59 Leninsky Prospekt, 11 7333 Moscow, Russia
Stephen Ducharme, University of NebraskaFollow
Peter A. Dowben, University of Nebraska-LincolnFollow

Date of this Version

6-29-2000

Comments

Submitted for the Proceedings of the 10th International Conference in Solid Films and Surfaces (ICSFS-lo), Princeton, Jul. 9-13,2000.

Abstract

We present evidence for a change in electron - phonon coupling across a bulk phase transition. Below the lattice stiffening transition at around 160 K, there is a change in the diffracted peak width observed by neutron and X-ray scattering techniques. Also, the electronic band structure of the copolymer is shifting in binding energy below 160 K, decreasing the density of states near the Fermi level. The value of the effective Debye temperature above the transition temperature is approximately 50 K, while below 160 K, the value of the Debye parameter is 245 K. We postulate that the coupling between electrons and phonons results in a static distortion of the lattice (below 160 K), and this distortion "melts" above 160 K.