Physics of polymeric ferroic devices
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Abstract
Functional polymers are macromolecules with unique and sometimes combined physical
For example, poly vinylidene fluoride-co-trifluoroethylene, P(VDF-TrFE), is a well-known
copolymer that is nearly a perfect insulator but also possesses piezoelectricity, a bidirectional property.
Upon applying an exerted mechanical stress, electric charges with opposite polarity
poles. Similarly, applying a time-variant electric potential difference induces mechanical
structure of the material. P(VDF-TrFE) is also ferroelectric and belongs to a sub-category of
materials that can retain their electric polarizations even after removal of the applied
field. Consequently, P(VDF-TrFE) has been envisioned for energy harvesting, information
multiferroic applications.
In the first three chapters of this thesis, we demonstrate a proof-of-concept single transistor
memory element using graphene as the semiconductor channel of a field-effect transistor
P(VDF-TrFE) is used as the ferroelectric gate insulator. Besides the details of reproducible
fabrication, an experimentally validated device model is presented that can be used for
memory elements based on ferroelectric graphene field-effect transistors for information
neuromorphic applications. The model serves as the basis for understanding of the
transistors.
In the remaining chapters, voltage generation in piezoelectric P(VDF-TrFE) films is
finite-element analysis method, we investigate some strategies to improve the power output
piezoelectric layers made of P(VDF-TrFE). Porosity is suggested and experimentally
procedure for improving the voltage output in piezoelectric layers. The findings can be
polymer-based multiferroic composites systems to boost their magnetoelectric coupling coefficients.
Finally, the thesis demonstrates multiferroic capacitors based on nanocomposite thin-films
and magnetic nanoparticles. For the first time, the theory related to magnetoelectric
measurements of multiferroics using a lock-in technique is presented and the internal
method is experimentally validated. Finally, through experimental investigation and finite
modelling, a detailed study of the polymer-based multiferroic thin-films is presented and
extensively.