Morphology,annealing,and melting of ferroelectric langmuir-blodgett films of vinylidene fluoride (70) trifluoroethylene (30) copolymer

摘要

We report an investigation of the effects of film thickness,deposition pressure,and annealing conditions on morphology and crystal structure of films of vinylidene fluoride (70% mol) and trifluoroethylene (30% mol) copolymer made by Langmuir-Blodgett (LB) deposition on silicon.The films were characterized with X-ray diffraction,electron microscopy,electron diffraction,and atomic force microscopy.The films are highly planer,with the polymer chains parallel to the film plane.The optimum deposition pressure range is 3-10 mN/m.Annealing at 120-135 degC in the paraelectric phase improves film crystallinity in the ferroelectric beta phase,with (110) orientation.The film thickness has a small effect on film morphology,and very little effect on crystallinity.Melting the films at 150 degC results in destruction of the (110) crystallites and grwth of 6mumX0.3mum lamella-like structures with a different orientation.This results in polymer chain segments tilted out of the film plane,as confirmed by infrared ellipsometry.