We report on the coupling between ferroelectric and magnetic order parameters in a nanostructured BaTiO3-CoFe2O4 ferroelectromagnet. This facilitates the interconversion of energies stored in electric and magnetic fields and plays an important role in many devices, including transducers, field sensors, etc. Such nanostructures were deposited on single-crystal SrTiO3 (001) substrates by pulsed laser deposition from a single Ba-Ti-Co-Fe-oxide target. The films are epitaxial in-plane as well as out-of-plane with self-assembled hexagonal arrays of CoFe2O4 nanopillars embedded in a BaTiO3 matrix. The CoFe2O4 nanopillars have uniform size and average spacing of 20 to 30 nanometers. Temperature-dependent magnetic measurements illustrate the coupling between the two order parameters, which is manifested as a change in magnetization at the ferroelectric Curie temperature. Thermodynamic analyses show that the magnetoelectric coupling in such a nanostructure can be understood on the basis of the strong elastic interactions between the two phases.

Ambipolar transport behavior in isoindigo-based conjugated polymers is observed for the first time. Fluorination on the isoindigo unit effectively lowers the LUMO level of the polymer and significantly increases the electron mobility from 10(-2) to 0.43 cm(2) V(-1) s(-1) while maintaining high hole mobility up to 1.85 cm(2) V(-1) s(-1) for FET devices fabricated in ambient. Further investigation indicates that fluorination also affects the interchain interactions of polymer backbones, thus leading to different polymer packing in thin films.

BiFeO 3 was studied as an alternative environmentally clean ferro/piezoelectric material. 200-nm-thick BiFeO 3 films were grown on Si substrates with SrTiO 3 as a template layer and SrRuO 3 as bottom electrode. X-ray and transmission electron microscopy studies confirmed the epitaxial growth of the films. The spontaneous polarization of the films was ϳ45 C/cm 2 . Retention measurement up to several days showed no decay of polarization. A piezoelectric coefficient ͑d 33 ͒ of ϳ60 pm/ V was observed, which is promising for applications in micro-electro-mechanical systems and actuators.

For the first time, ambient-stable and balanced carrier transport is achieved in polymer ambipolar fieldeffect transistors (FETs) and inverters with high performance. With chlorinated isoindigo polymers, FETs fabricated in ambient conditions show hole mobilities up to 0.81 cm 2 V À1 s À1 and dramatically increased electron mobilities from 10 À2 to 0.66 cm 2 V À1 s À1 . Hence, chlorination is effective to modulate electronic properties and improve the device performance of conjugated polymers.

We demonstrate that a near-field microwave microscope based on a transmission line resonator allows imaging in a substantially wide range of frequencies, so that the microscope properties approach those of a spatially-resolved impedance analyzer. In the case of an electric probe, the broadband imaging can be used in a direct fashion to separate contributions from capacitive and resistive properties of a sample at length scales on the order of one micron. Using a microwave near-field microscope based on a transmission line resonator we imaged the local dielectric properties of a Focused Ion Beam (FIB) milled structure on a high-dielectric-constant Ba 0.6 Sr 0.4 TiO 3 (BSTO) thin film in the frequency range from 1.3 GHz to 17.4 GHz. The electrostatic approximation breaks down already at frequencies above ~10 GHz for the probe geometry used, and a full-wave analysis is necessary to obtain qualitative information from the images.