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The features of ferroelectric materials and their applications are presented. State-of-the-art employment of characterization techniques, and the properties of ferroelectric materials are described. Classification of ferroelectric materials, phase transitions, and diffuse phase transition (DPT) have been discussed. Properties of ferroelectrics, polarization-field hysteresis, dielectric hysteresis, reversal of spontaneous polarization, and dielectric properties have been explained. Besides these, piezoelectric and pyroelectric properties of materials have also been demonstrated. The applications of ferroelectric thin films have been discussed with a specific focus on acousto-optic (AO) properties and their applications. [ABSTRACT FROM AUTHOR]

The evolution of device miniaturization and the potential application for next-generation nonvolatile memory devices Pb(Zr0.53Ti0.47)0.60(Fe0.5Ta0.5)0.40O3 (PZTFT) can be used as a barrier in multiferroic tunnel junctions. We report single-phase magnetoelectric multiferroic ultra-thin PZTFT at room temperature. The magnetic and ferroelectric properties have been investigated down to 7 nm thickness which are requisite properties for multiferroic tunnel barriers for multi-states memory applications. In the present study, we show that it remains a switching multiferroic at room temperature down to at least thickness d = 7 nm, which is thin enough for tunnel junctions. [ABSTRACT FROM AUTHOR]

Magnetoelectric multiferroics, because of their coupled electric and magnetic ordering in a single phase, are eminent for applications in logic and nonvolatile memory devices. Recent advances in computational modeling, synthesis, and characterization techniques are spurring significant advances in the study of these materials. During last several years, our group at University of Puerto Rico has been involved in synthesizing novel single-phase room temperature multiferroic materials that included not only solid solutions of lead zirconate titanate with lead iron tungstate, lead iron niobate, and lead iron tantalate, but also recently discovered palladium substituted room temperature multiferroics, namely PbPd0.3Ti0.7O3 and Pb(Zr0.2Ti0.8)Pd0.3O3. In this review, we have reported thin films of the above materials that were synthesized using pulsed laser deposition technique on various substrates at Speclab, University of Puerto Rico. We describe in detail thin film fabrication, structural diffraction analyses (XRD, TEM), dielectric, ferroelectric, piezo-response force microscopy, and magnetization results on recently grown Pd-substituted lead titanate and lead zirconate titanate thin films in an elaborate manner. The films were phase pure and stabilized in c-axis oriented tetragonal phase (P4mm) with surface roughness RQ of 2–4 nm. Temperature-dependent dielectric studies on metal-dielectric-metal heterostructure capacitors indicate that ferroelectric to paraelectric phase transition is above 500 K. A proof of ferroelectricity was confirmed from strong domain switching responses using piezo-response force microscopy. These films showed ferromagnetic ordering below 395 K. The origin of magnetic ordering in these materials was attributed to the existence of Pd2+ and Pd4+ mixed oxidation states of palladium dispersed in the polar matrices. We conclude with the above findings that these multiferroics may have potential applications.in nonvolatile memory and other multifunctional devices. [ABSTRACT FROM AUTHOR]

Ba0.70Sr0.30TiO3-(BST) ceramics were fabricated by conventional mixed oxide route. The structural phase transition, ferroelectric, dielectric and energy storage properties of BST ceramics capacitors were investigated. Electric field induced weak ferroelectricity is observed for BST ceramics. Temperature dependent dielectric property measurements of BST solid-solutions have shown a high dielectric constant and low dielectric loss. Room temperature breakdown field strength and energy densities were obtained from P-E loops. The recoverable energy density is 0.17 J/cm3with dielectric breakdown strength as high as 150 kV/cm. BST ceramics have shown interesting energy densities; these might be the strong candidate materials for capacitor applications. [ABSTRACT FROM AUTHOR]

Temperature stability of voltage tunability and figure of merit (FOM) were investigated for the pulsed laser deposited Ba0.6Sr0.4TiO3(BST0.6) thin films on platinum coated silicon [Pt(111)/TiOx/SiOx/Si(100)] substrates. The structural and micro-structural properties of these films were analyzed using x-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Metal-ferroelectric-metal (MFM) mono-dielectric layer stacks were fabricated using these films and their temperature and voltage dependent dielectric properties were quantified. The temperature dependence of dielectric properties were analysed using the modified Curie-Weiss law. The films showed a good dielectric tunability of about 40% at a bias field of 125 kV/cm. The determined figure of merits are found to be highly sensitive to the temperature changes. The observed ferroelectric-like behaviour in these films above the Curie point (Tc) has been attributed to the thermal expansion mismatch and the substrate induced misfit strain with the Pt/Si substrate. [ABSTRACT FROM PUBLISHER]

The bismuth layer structured ferroelectric (BLSF) ceramics consisting of four-layers (BaLa0.75Bi3.25Ti4O15) and five-layers (Ba2La0.75Bi3.25Ti5O18) were prepared by the conventional solid-state reaction method. Summerfield ac-conductivity scaling analysis was used to evaluate the electrical behavior and the ac-conductivity isotherm curves. The relaxation results were corroborated with the Raman Peak positions and full width at half maximum was obtained by using Lorentzian peak fit method. Finally, the results were compared with the two-layered relaxor-compound (Bi2.45La0.55TiNbO9) and technologically standard three-layered compounds (La0.75Bi3.25Ti3O12; BLT). The dielectric relaxation of Bi2.45La0.55TiNbO9was verified using modified Curie-Weiss law and Vögel-Fulcher relationship. An attempt is made to realize the typical collective nature of the ionic conductivity of the samples. [ABSTRACT FROM AUTHOR]

In the last decade, a tremendous amount of research works have been carried out in the area of multiferroic nanostructure materials in order to meet the requirement of science and technology for the future microelectronic industries. The potential functionalities of any kind nanostructure materials lies in the vicinity of large surface to volume ratio compare to the bulk counterpart. The new technology for microelectronics require small dimension, robust mechanical properties, higher degree of electrical and electronic properties and finally high output power with low dissipation energy. The area of ferroelectric and multiferroic nanostructures are vast, this chapter deals with the different variety of multiferroic nanostructure with different dimensionality (D) 0D 1D, 2D and 3D and their state of art characterization process. Possible and feasible theoretical modeling and related experimental facts of already established multiferroics nanostructures will be described. It will also cover the advantages and the limitations of these nanostructures in design, development, and particularly for device applications. [ABSTRACT FROM AUTHOR]

Ba0.70Ca0.30TiO3-(BCT),Ba(Zr0.2Ti0.8)O3-(BZT) ceramics were fabricated by conventional mixed oxide route to develop inorganic dielectric materials suitable for use as an insulator with high dielectric constant and low energy loss for capacitor applications. The structural phase transition, ferroelectric, dielectric and energy storage properties of BCT, BZT ceramic capacitors were investigated. Room temperature X-ray diffraction (XRD) patterns revealed prominent peaks corresponding to tetragonal perovskite crystal structure for both BCT, BZT solid solutions. Slim ferroelectric hysteresis (P-E) loops were observed for BCT, BZT solid solutions. Temperature dependent dielectric property measurements of BCT, BZT solid solutions have shown a high dielectric constant and low dielectric loss. Room temperature (300K) breakdown field strength and energy densities were obtained from the integral area of P-E loops. For the BCT ceramics, the largest recoverable energy (unreleased energy) density is 1.41 J/cm3with dielectric breakdown strength as high as 150 kV/cm. For the BZT ceramics, the largest recoverable energy (unreleased energy) density is 0.71 J/cm3with dielectric breakdown strength as high as 150 kV/cm. Bulk BCT, BZT ceramics have shown interesting energy densities; these might be the strong candidate materials for capacitor applications. [ABSTRACT FROM AUTHOR]

We report enhancement of photovoltaic properties of highly oriented BiFeO3(BFO) thin films. The single phase rhombohedral R3c space group structure was confirmed by XRD and Raman spectra in the films grown on SrTiO3(111) substrates using RF magnetron sputtering. The films of BFO were characterized in planar geometry with top Pt electrodes having 200μm diameter, ∼40nm thickness and at a regular spacing of ∼150μm deposited by DC sputtering process. For photovoltaic studies the current voltage characteristic of as grown and poled samples were studied under the white light illumination having energy density of ∼1kW/m2. The as grown films showed open circuit voltage (Voc) of ∼3.9V which increased up to ∼17.8V on poling with 200V. This enhancement in Voc by poling was attributed to increase in net polarization due to alignment of domains in the direction of applied electric field and hence potential barriers between the domains. [ABSTRACT FROM AUTHOR]

The unipolar resistive switching characteristics of the amorphous LaLuO3thin films deposited by pulsed laser deposition have been studied. Reliable and repeatable nonvolatile switching of the resistance of LaLuO3films was obtained between two well defined states of low and high resistance with nearly constant resistance ratio ∼107and non-overlapping switching voltages in the range of 0.66-0.83 V and 1.9-2.7 V respectively. The temperature dependent measurement revealed metallic and semiconducting behavior in low and high resistance states respectively. The switching between low and high resistance states was attributed to the change in the separation between oxygen vacancies in light of the correlated barrier hopping theory. The current conduction mechanism of the device in high-resistance state followed the Poole's law, whereas the conduction in low-resistance state was found to be dominated by percolation. The resistance of low and high resistance states of the film showed no obvious degradation for up to ∼104seconds indicating good retention. The achieved characteristics of the resistive switching in LaLuO3thin films seem to be promising for futuristic nonvolatile memory applications. [ABSTRACT FROM AUTHOR]

(PbZr0.53Ti0.47O3)(1-x)-(PbFe0.5Ta0.5O3)x, (PZTFT, x = 0, 0.1, 0.2, 0.3, 0.4, 1) ceramics were prepared by conventional solid state reaction route. X-ray diffraction patterns and Raman spectra revealed the formation of single phase tetragonal crystal structure at ambient temperature. With increase of Pb(Fe0.5Ta0.5)O3 (PFT) composition in PZTFT matrix significant enhancement in the grain size was observed where average grain sizes were in the range of 1-15 μm. Naturally designed PZTFT composites show higher dielectric constant than Pb(Zr0.53Ti0.47)O3 (PZT) but less than PFT. The ferroelectric (FE) to paraelectric (PE) phase transition temperature i.e. Curie temperature (Tc) shifted towards lower temperature side with increase in iron and tantalum compositions. Both polarization and magnetic moment were observed at room temperature in all PZTFT (x ≥ 0.2) composites suggesting multiferroic characteristic in these systems. Significant improvement of the ferroic properties were observed with increase of PFT concentration. [ABSTRACT FROM AUTHOR]

PbZr0.53Ti0.47O3/CoFe2O4 multilayer nanostructures were grown on La0.5Sr0.5CoO3 coated MgO and Pt/TiO2/SiO2/Si substrates by pulsed laser deposition. Ferroelectric polarization decreased slowly in reducing the temperature from 300 to 200 K, with complete collapse of polarization at 100 K, but there was complete recovery of the polarization during heating. At the same time, the temperature dependent remanent magnetization of the multilayer nanostructures showed slow enhancement in the magnitude till 200 K with three-fold increase at 100 K compared to room temperature. Thus the enhancement in remanent magnetization and the decrease in polarization on lowering the temperature suggest that dynamic the magnetoelectric coupling existed in the multilayer systems. [ABSTRACT FROM AUTHOR]

The magnetic properties of BiFeO3(BFO) - CoFe2O4(CFO) heterostructure thin films, grown on (100), (110) and (111) SrTiO3 (STO) substrates by employing pulsed laser deposition (PLD) method, have been studied. The XRD patterns of BFO-CFO multilayer thin films compared with the pure CFO and BFO thin films grown using under identical conditions evidenced that all peaks present correspond to CFO and BFO structure in two separate phases. Micro-Raman spectra analysis also reveals the presence of BFO and CFO in two separate phases in the heterostructures thin films. The anomalous enhancement in magnetization has been observed for BFO-CFO multilayer thin films, relative to pure BFO thin films in all three different orientations. The saturation magnetization for (100), (111) and (110) oriented BFO-CFO thin films are 44, 62 and 80 emu/cc suggesting that (110) is most preferable direction to achieve the magneto electric (ME) coupling effect. [ABSTRACT FROM AUTHOR]

PbSc0.5Nb(1 -x)/2Tax/2O3(PSNT for x = 0.3, PST for x = 1) nanoceramics and thin films were prepared by high energy ball mill with solid state reaction technique and pulse laser deposition (PLD) respectively. A comparative study of the microstructure, dielectric properties, and polarization of PSNT and PST thin films and nano ceramics were carried out over a wide range of temperature (100 K-600 K) and frequency (100 Hz to 1 MHz). High Resolution Transmission Electron Microscopy (HRTEM) image of PSNT and PST thin films indicate the presence of small polar nano regions (PNRs) and long range ordered regions in crystal lattice plane respectively. PST nanoceramics (PST-N) showed normal ferroelectric behavior where as its thin film form (PST-F) illustrated relaxor behavior. PSNT nanoceramics (PSNT-N) and its films (PSNT-F) demonstrated weak frequency dispersion and strong frequency dispersion in dielectric spectra respectively. A shift in dielectric maximum temperature (Tm) towards lower temperature side i.e. 65 K and 85 K were observed for PSNT-F and PST-F compare to their nanoceramices indicates greater role of substrate-electrode-interface strain on dielectric properties. Well behaved hysteresis at room temperature for PSNT-F point toward strong competition between short range order and long range order. A weak slim hesteresis for PST-F were observed at room temperature suggesting the existence of polar nano regions far above dielectric maximum temperature. [ABSTRACT FROM AUTHOR]

Thin films of BaZr0.25Ti0.75O3 in which Ba2 + is partially substituted by Ca2 + are prepared by a sol-gel method. Phases and dielectric properties of the films are studied.The crystal structure of BaZr0.25Ti0.75O3 is cubic and does not change with Ca substitution upto x = 0.25 in Ba1-xCaxZr0.25Ti0.75O3. A change from a normal to relaxor behavior is observed for x = 0.20 as indicated by a change in the frequency of dielectric maxima with temperature and other parameters.The dielectric constant and transition temperatures are found to increase with increasing Ca substitution. A tunabilty of 71%, much higher than reported in literature for this material, is observed for x = 0.1 i.e for Ba0.9Ca0.1Zr0.25Ti0.75O3. [ABSTRACT FROM AUTHOR]

BaTiO 3 /SrTiO 3 superlattices were grown on (001)MgO substrates by pulsed-laser-deposition technique. The thickness of each layer varied from 6 to 25 unit cells. Polarization-dependent Raman spectra confirmed tetragonal symmetry of the superlattices with the polar axis being normal to the layers. The observed optic modes in the superlattices showed intermediate frequencies between corresponding bulk BaTiO 3 and SrTiO 3 values, while the E( TO 1 ) soft mode exhibited upward shift due to significant two-dimensional clamping caused by the lattice mismatch of the constituting layers. The observed downward shift of the soft mode revealed relaxation of two-dimensional stresses with increasing the stacking periodicity of the superlattices. The excitation of folded transverse acoustic phonons in the Raman spectra due to the new periodicity of the Brillouin zone was revealed. The observed data are quantitatively explained by a folding of the corresponding acoustic branch. It is shown that micro-Raman spectroscopy provides determination of a spatial variation of the layer thickness in graded superlattices. [ABSTRACT FROM AUTHOR]

Bi-layered ferroelectric thin films of (Sr 0.8 Ba 0.2 )Bi 2 Ta 2 O 9 were grown on Pt/TiO 2 /SiO 2 /Si substrates using the pulsed laser deposition technique. The effect of oxygen pressure and annealing temperature on the structural and electrical properties were studied. The XRD results revealed that the films grown at lower oxygen pressure (100-200 mTorr) and annealed at higher temperature (>800 °C) have the evidence of secondary phase. Whereas, films grown at higher pressure (300 mTorr) and annealed at higher temperature ∼850 °C does not show any secondary phases. Increase in the intensity of optical phonon modes with annealing temperature is attributed to larger grain size at higher annealing temperatures. The films annealed at 800 °C show enhanced ferroelectric properties with remanent polarization (2P r ) of 23.5 μC/cm 2 and coercive field of ∼31 kV/cm. The Films annealed at higher temperature (800°C) have relatively higher dielectric constant with lower dissipation factor (∼0.02). Increased tangential loss with the annealing temperature (> 800 °C) is attributed to the interdiffusion of Bi in to Pt electrode. [ABSTRACT FROM AUTHOR]

Information on the International Symposium on Integrated Functionalities (ISIF) in San Juan, Puerto Rico on June 13-16, 2010 is presented. Topics include the science of high-dielectric constant and ferroelectric thin films, integration of materials, and the fabrication and design of advanced devices. The symposium featured various professionals from academia, companies, and national laboratories.