A nonvolatile highly scalable multilevel memory based on ferroelectric domain walls is demonstrated.

The p-type BiCuOCh (Ch ¼ S, Se and Te) compounds exhibit very low lattice thermal conductivities and moderate power factors in the medium temperature range, resulting in high thermoelectric figures of merit. In this paper, we investigated their electronic structures using density functional theory, and discovered that a mixture of heavy and light bands near the valence band maximum is beneficial for good thermoelectric performance, and the Cu 3d-Ch np antibonding state near the valence band edge determines the transport properties of BiCuOCh. Semi-classic Boltzmann transport theory was then used to calculate the Seebeck coefficients, electrical conductivities and power factors of BiCuOCh, and the optimal doping concentrations were estimated based on the predicted maximum power factors. The temperature dependence of the thermoelectric transport properties of BiCuOSe were also estimated and compared with experimental data, with good agreement observed.

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Polymer ferroelectrics are flexible and lightweight electromechanical materials that are widely studied due to their potential application as sensors, actuators, and energy harvesters. However, one of the biggest challenges is their low piezoelectric coefficient. Here, we report a mechanical annealing effect based on local pressure induced by a nanoscale tip that enhances the local piezoresponse. This process can control the nanoscale material properties over a microscale area at room temperature. We attribute this improvement to the formation and growth of β-phase extended chain crystals via sliding diffusion and crystal alignment along the scan axis under high mechanical stress. We believe that this technique can be useful for local enhancement of piezoresponse in ferroelectric polymer thin films.

Development of magnetoelectric, electromechanical, and photovoltaic devices based on mixed-phase rhombohedral-tetragonal (R-T) BiFeO(3) (BFO) systems is possible only if the control of the engineered R phase variants is realized. Accordingly, we explore the mechanism of a bias induced phase transformation in this system. Single point spectroscopy demonstrates that the T → R transition is activated at lower voltages compared to T → -T polarization switching. With phase field modeling, the transition is shown to be electrically driven. We further demonstrate that symmetry of formed R-phase rosettes can be broken by a proximal probe motion, allowing controlled creation of R variants with defined orientation. This approach opens a pathway to designing next-generation magnetoelectronic and data storage devices in the nanoscale.