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The growing need to process a diverse range of data has ignited effort in developing new multifunctional logic gate devices. In this article, we report a new form of all-in-one logic gate system that exploits the photoresponsivity of a self-powered multifunctional BiFeO3 (BFO) sensor material. The BFO sensor can not only detect both light intensity and temperature, but it can also execute three common logic gates of “AND”, “OR”, and “NOT” by converting optical and thermal inputs into electrical output. The diverse functionality of the BFO logic gate sensor array utilizes the unique light-and temperature-controlled energy band structure and carrier behavior of the BFO material. To demonstrate the potential, a 3 × 3 logic gate sensor matrix is developed, which successfully detected light and temperature distributions, and accurately produced the three basic logic gate operations. This work provides a new route to construct highly integrated multifunctional electronic devices for the advancement of large sensing, communication, and computing operations. (Figure presented.).

When scaling the lateral size of a ferroelectric random access memory (FeRAM) device down to the nanometer range, the polarization switching-induced displacement current becomes small and challenging to detect, which greatly limits the storage density of FeRAM. Here, we report the observation of significantly enhanced injection currents, much larger than typical switching currents, induced by polarization switching in BiFeO3 thin films via conductive atomic force microscopy. Interestingly, this injected current can be effectively modulated by applying mechanical force. As the loading force increases from ∼50 to ∼750 nN, the magnitude of the injected current increases and the critical voltage to trigger the current injection decreases. Notably, changing the loading force by an order of magnitude increases the peak current by 2-3 orders of magnitude. The mechanically boosted injected current could be useful for the development of high-density FeRAM devices. The mechanical modulation of the injected current may be attributed to the mechanical force-induced changes in the barrier height and interfacial layer width.

Este trabajo reporta la síntesis y caracterización de los sistemas y , obtenidos por el método de reacción de estado sólido. Los óxidos obtenidos se caracterizarón por difracción de rayos X (DRX), refinamiento Rietveld y medidas de magnetización en función del campo magnético aplicado y la temperatura. La caracterización estructural por DRX y refinamiento Rietveld permitió la identificación de este material, el cual posee estructuras tipo perovskita romboédral con grupo espacial R3c. La caracterización por microscopía electrónica de barrido (MEB) permitió determinar que los sólidos sintetizados presentan una microestructura homogénea. Las curvas de magnetización en función del campo magnético externo se trabajaron en el rango de 500 y 1000 Oe se midieron a temperaturas de 50 y 300 K, los sólidos sintetizados exhibieron un comportamiento ferromagnético, con aumento de la magnetización remanente (MR), el campo coercitivo (HC) y la susceptibilidad magnética cuando se aumenta la concentración de Samario. Las características estructurales y magnéticas que se generan en los sólidos obtenidos hacen a estos materiales de gran interés como componentes multiferroicos. This work reports synthesis and characterization of the systems and , produced by the solid-state reaction method. The oxides obtained was characterized by X ray diffraction (XRD), Rietveld refinement and magnetization measures in function of the magnetic field applied and temperature. The structural characterization by Rietveld refinement and XRD allow identification perovskite type structure on all the materials with rhombohedral crystalline system and R3c space group. The characterization by scanning electron microscope (SEM) allow determinate that the sintered solids present a homogenous microstructure. The magnetization curves in function of magnetic field applied between 50 and 300 K and in function of the temperature between 500 and 1000 Oe of the sintered solids exhibited a ferromagnetic behavior, with a rise of the permanent magnetization (MR), the coercive field (HC) and the magnetic susceptibility when the samarium concentration rise up. The structural and magnetic characteristic that are generated in the obtained solids make these materials to big interest as multiferroic components. Ingeniero Electronico Pregrado

BiFeO3 is an interesting multiferroic material with potential use in sensors and transducers. However, the high coercive field and low dielectric strength of this material make the poling process extremely difficult. Poling becomes a lot easier if the ceramic particles are incorporated in a non-conductive polymer with comparable dielectric properties. In this work, unstructured composites consisting of BiFeO3 particles in a non-piezoactive PVDF terpolymer matrix are made with a ceramic volume fraction ranging from 20% to 60%. The highest piezoelectric charge and voltage constant values (d33 = 31 pC/N and g33 = 47 mV m/N) are obtained for a BiFeO3-PVDF terpolymer composite with a volume fraction of 60%. The Poon model is chosen to analyse the volume fraction dependence of the dielectric constant while the modified Yamada model is used to analyse the piezoelectric charge constant data. It is concluded that the maximum possible piezoelectric constant for bulk BiFeO3 can be as high as 56 pC/N.

This work reports the morphological and chemical characterization of multiferroic BiFeO 3 polycrystalline thin films grown on Si(111) by RF-sputtering. Results are shown for a large set of samples and a wide array of experimental techniques, including imaging (atomic/piezoresponse force microscopy) and spectroscopic (μ-Raman, X-ray photoemission, X-ray diffraction) probes. Through growth and post-growth annealing treatment, a fine control over stoichiometry, grain size, grain orientation, crystal order and surface roughness is achieved. In particular, the grain size can be tailored from nanocrystals to large micrometric plates as a function of the annealing temperature. For the optimal stoichiometric sample, an additional X-ray absorption and magnetic circular dichroism analysis has been carried out, which provides high quality spectra comparable with epitaxial films and further proves the expected strong local antiferromagnetic order.

Single-phase multiferroic BiFeO3 (BFO) powders were prepared by hydrothermal microwave synthesis and dense BiFeO3 ceramics were fabricated for the first time by the low-temperature high-pressure (LTHP) sintering technique. Effect of sintering temperature ranging from 400 to 800 degrees C (3min and 10min) and pressure of 3-8 GPa on structural, microstructural, electric and magnetic properties were investigated through X-ray diffraction, scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), density and magnetic measurements. The results highlighted that LTHP sintering method, thanks to the high pressure involved, requires lower temperature and shorter time than other techniques, avoiding BiFeO3 phase degradation. SEM images show that for short experimental time (t = 3min) the average grain size of the sintered samples was approximately the same size of raw powder. Extending the sintering time up to 10min the grain growth phenomena occurred. Moreover the results indicate that the best obtained density value was around 98% of theoretical density. The dielectric behavior of BiFeO3 ceramics was not significantly influenced by the LTHP sintering conditions. Magnetic measurements showed that ceramic BiFeO3 is weakly ferromagnetic at room temperature.

Pyroelectric materials are very promising for thermal energy harvesting applications. To date, lead-based systems are the foremost studied materials in this field. A facile and simple metal organic chemical vapor deposition route is applied for the fabrication of lead-free, high quality, epitaxial Bi(1-x)DyxFeO3 (x = 0, 0.06, 0.08, 0.11) thin films deposited on conductive SrTiO3:Nb (100) single crystal substrates. The films are studied by structural, morphological, compositional, and functional characterization. The correlation between the Dy-doping amount and the dielectric properties is thoroughly investigated. Unipolar polarization-electric field loops and permittivity measurements show the important impact of Dy on ferroelectric, dielectric, and pyroelectric properties. Dy doping increases considerably the dielectric response, but much more the pyroelectric coefficient, up to a concentration of 8% Dy. The films are self-poled, which is an ideal situation for pyroelectric applications. The best figure of merit for pyroelectric energy harvesting, F-E, is 82 J m(-3) K-2, showing a factor increase of 2.6 as compared to the undoped film of the sample series. It constitutes a factor 4.5 improvement as compared to previous results obtained on BiFeO3 based thin films.