Recent developments in ferroelectric nanostructures and multilayers

Abstract

The property of ferroelectricity was first reported in 1921 in Rochelle salt (sodium potassium tartrate). Once considered a rare phenomenon limited to a comparatively small class of crystals, the discovery of ferroelectricity in the binary oxide compound barium titanate (BaTiO 3 ) in the mid-1940s paved the way for rapid advances in the search of new materials. Since that time, a great many other ferroelectric compounds and solid solutions have been found and there has been broad interest in ferroelectric materials that has continued essentially uninterrupted until the present time. Ferroelectric materials remain subjects of intensive investigation today for three principal reasons. First, the unique dielectric, pyroelectric, piezoelectric, and electro-optic properties exhibited by ferroelectric crystals, ceramics, composites, and thin films can be exploited in great many devices of commercial importance. Second, apart from their many technological applications, ferroelectric materials as a class exhibit a great diversity of phase transitions that make them ideal objects for scientific investigations into the origins and mechanisms of a wide range of structural transformation phenomena. Finally, advances in thin-film deposition and nanoscale fabrication techniques made over the past two decades have created new possibilities for the integration of these materials into the ever expanding array of microelectronic devices.Ferroelectrics form a sub-group of functional (or smart) materials whose physical properties are sensitive to changes in external conditions such as temperature, pressure, and electric fields. Below some critical temperature T C , the dielectric displacement (electric polarization) spontaneously assumes non-zero values in the absence of any externally applied force. The transition between non-ferroelectric and ferroelectric phases is accompanied by a loss of symmetry, characterized by double-well minima below the transition temperature, resulting in a switchable polarization that is accompanied by a hysteresis in the electric field-dielectric displacement response. As a class of materials, ferroelectrics also exhibit unusually large and nonlinear generalized susceptibilities; their dielectric, piezoelectric, elastic, and other properties display critical behavior near the ferroelectric phase transformation temperature. Ferroelectrics may be regarded as high energydensity materials as well that can be configured to store, release or interconvert electrical and mechanical energy in a well-controlled manner. Their exceptionally large piezoelectric compliances, pyroelectric coefficients, and dielectric susceptibilities can be exploited in a variety of microelectronic devices. Important examples of these include piezoelectric sensors and actuators, pyroelectric thermal imaging devices, high-dielectric constant capacitors, electro-optic light valves, and thin-film memories. Because of their strongly non-linear dielectric response ferroelectrics can be utilized in applications such as frequency-agile pha...

Effect of lattice mismatch on the magnetic properties of nanometer-thick La0.9Ba0.1MnO3 (LBM) films and LBM/BaTiO3/LBM heterostructures

“…In heterostructures the substrate/film interfaces or ferromagnetic/ferroelectric interfaces become critically important for technological applications. Previous studies have showed the effect of misfit strain caused by lattice mismatch on magnetic and electric properties of films and heterostructures [4].…”

“…Since the observation of colossal magnetoresistance (CMR) effect in La-doped manganese oxides, they have been extensively investigated [5][6][7]. La1−xAExMnO3 (AE = alkaline earth) present a wide range of crystal structure and functionalities [2,[8][9][10]4]. The overlap between Mn d orbitals and oxygen p orbitals produces an electronically active band, which can be influenced by the internal stress caused by AE-site substitution [11].…”

“…BaTiO3 as a traditional ferroelectric is known for its unique piezoelectric behavior, which its diversity of phase transition makes it ideal for scientific research on mechanisms of wide range of structural transition phenomena [4,19,20].…”

Phase-field modeling of the influence of domain structures on the electrocaloric effects in PbTiO3 thin films

“…Ferroelectrics in the form of thin films have attracted tremendous interests from many researchers over the last two decades due to the rapid development of nanoscale fabrication techniques that contribute to the novel properties of thin films [17]. In the study of ECEs, ferroelectrics in the form of thin films have been extensively studied due to their much higher dielectric strength over the bulks, which contributes to giant ECEs [18,19].…”

Flexible Ferroelectric BaTiO3 – PVDF Nanocomposites

“…Their exceptionally large piezoelectric compliances, pyroelectric coefficients, dielectric susceptibilities and electro-optic properties make them very attractive for nanotechnologyrelated applications such as high energy density capacitors, pyroelectric thermal imaging devices, gate insulators in transistors, electro-optic light valves, thin-film memory elements, multiferroic transducers, energy harvesters, etc. (Alpay et al, 2009, Nonnenmann & Spanier, 2009Scott, 2007;Leionen et al, 2009) The most common ferroelectric materials in commercial applications are ceramics, such as lead zirconate-titanate (PZT), barium titanate (BTO), calcium-copper titanate CaCu 3 Ti 4 O 12 (CCTO), sodium niobate (NaNbO 3 ), among others, which present a high dielectric constant, high dipole moment and high electromechanical coupling coefficient. Ferroelectric ceramics have been recently synthesized by solvothermal (Wada et al, 2009), coprecipitation (Hu, et al, 2000), sol-gel (Kobayashi et al, 2004), and template assisted methods (Rorvik et al, 2009), in order to obtain nanostructured materials.…”