AVS 46th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Monday Sessions
       Session AS+MI+VM-MoM

Paper AS+MI+VM-MoM11
Phase Transitions in Two-dimensional Ferroelectric Films

Monday, October 25, 1999, 11:40 am, Room 610

Session: Magnetic Recording: Chemical Integration and Tribology
Presenter: C.N. Borca, University of Nebraska, Lincoln
Authors: C.N. Borca, University of Nebraska, Lincoln
J. Choi, University of Nebraska, Lincoln
S. Adenwalla, University of Nebraska, Lincoln
P.A. Dowben, University of Nebraska, Lincoln
M. Poulsen, University of Nebraska, Lincoln
J.L. Robertson, Oak Ridge National Laboratory
V.M. Fridkin, Russian Academy of Science
S.P. Palto, Russian Academy of Science
N. Petukhova, Russian Academy of Science
S.G. Yudin, Russian Academy of Science
S. Ducharme, University of Nebraska, Lincoln
Correspondent: Click to Email
We studied ferroelctric copolymer films of vinylidene fluor ide with trifluoroethylene, P(VDF-TrFE) 70:30. The films exibit ferroelectric switching properties and can be used in a variety of piezoelectric devices. In addition to the first order ferroelectric to paraelectric bulk transition at 80 degrees C, we report two other phase transitions. One appears at 20 degrees C and is related entirely to a surface ferroelectric transition.@footnote 1@ The third transition around 150 degrees K is due to a stiffening of the lattice and a change in the bulk electronic structure. For P(VDF-TrFE), there is a negligible density of states at the Fermi level making this phonon related transition very unusual. This last transition was observed using neutron diffraction, @footnote 2@ X-ray diffraction, photoemission spectroscopy and EELS. The effective Debye temperature decreases from a value of about 250 K to 50 K with increasing temperature across the 150 K lattice stiffening transition. @FootnoteText@ @footnote 1@J. Choi, P.A. Dowben, S. Pebley, A.V. Bune, S. Ducharme, V.M. Fridkin, S.P. Palto, N. Petukhova, Phys. Rev. Lett. 80, 1328 (1998) @footnote 2@C.N. Borca, J. Choi, S. Adenwalla, Stephen Ducharme, P.A. Dowben, Lee Robertson, V.M. Fridkin, S.P. Palto, and N. Petukhova, Appl. Phys. Lett. 74, 347 (1999).