Research Projects

The transient negative capacitance in a mono-domain ferroelectric capacitor occurs near the coercive field (E_C) due to large redistribution of bound charges, compensating the depolarizing field. In a multi-domain ferroelectric system, the depolarizing field appears within a length scale of domain size, resulting in static negative capacitance. This negative capacitance can help overcome the fundamental energy barrier of 60 mV/decade in ultra-low power FET devices. In a ferroelectric-dielectric supercapacitor, it could result in a 3-4 times jump in energy density. The domain structure-negative capacitance correlation in a multi-domain ferroelectric capacitor allows tuning the negative capacitance for observing large energy density. This project proposes a disruptive design by developing a magnetoelectric multiferroic-dielectric electrostatic supercapacitor instead of a ferroelectric-dielectric electrostatic supercapacitor. This would enable engineering the ferroelectric domain structure within a multiferroic system by applying a magnetic field and tuning substrate-film combination and film thickness. Epitaxial thin films of multiferroic BiFeO₃ (and BiFeO₃-SrTiO₃ multilayers) on single crystal substrates such as SrTiO₃, LSAT, and NdScO₃ will be grown using spin coating techniques. The films will be characterized by XRD, TEM, AFM, PFM, MFM, and EFM to determine the extent of epitaxy, epitaxial strain, and ferroelectric domain structure. The energy and power density of the multiferroic-dielectric supercapacitor will be determined by cyclic voltametry.