Search

Lead zirconate titanate (PZT) microtubes were assembled onto pre-patterned substrates using dielectrophoresis of a colloidal suspension of microtubes dispersed in isopropyl alcohol. High aspect ratio tubes with an outer diameter of 2 μm and length of about 30 μm were prepared by vacuum infiltration of mesoporous silicon templates. An interdigitated electrode structure with gap sizes ranging from 2 μm to 15 μm was patterned on a silicon substrate via conventional lithography. This allowed a non-uniform alternating electric field to be generated. The influence of the electrode gap along with the effects of the waveform, amplitude and frequency of an applied signal on the dielectrophoretic assembly of PZT microtubes was investigated. A square wave signal of 5 V rms and 10 Hz was found to be the most effective in assembling the microtubes on a 12 μm electrode gap. The results show potential for the dielectrophoretic technique in realizing integrated 3D devices using the high aspect ratio piezoelectric tube structures as building blocks.

Piezoelectric thin films are of increasing interest in low-voltage micro electromechanical systems for sensing, actuation, and energy harvesting. They also serve as model systems to study fundamental behavior in piezoelectrics. Next-generation technologies such as ultrasound pill cameras, flexible ultrasound arrays, and energy harvesting systems for unattended wireless sensors will all benefit from improvements in the piezoelectric properties of the films. This paper describes tailoring the composition, microstructure, orientation of thin films, and substrate choice to optimize the response. It is shown that increases in the grain size of lead-based perovskite films from 75 to 300 nm results in 40 and 20% increases in the permittivity and piezoelectric coefficients, respectively. This is accompanied by an increase in the nonlinearity in the response. Band excitation piezoresponse force microscopy was used to interrogate the nonlinearity locally. It was found that chemical solution-derived PbZr(0.52)Ti(0.48)O(3) thin films show clusters of larger nonlinear response embedded in a more weakly nonlinear matrix. The scale of the clusters significantly exceeds that of the grain size, suggesting that collective motion of many domain walls contributes to the observed Rayleigh behavior in these films. Finally, it is shown that it is possible to increase the energy-harvesting figure of merit through appropriate materials choice, strong imprint, and composite connectivity patterns.

Impedance spectroscopy studies were conducted on amorphous tantalum oxide thin films prepared using pulsed-DC reactive sputtering, which were post-annealed to crystallize the films. X-ray diffraction results showed that crystallization to Ta2O5 β phase occurs for samples annealed above 650 °C, with a crystallite size of ∼40 nm. The film microstructure was studied by electron microscopy, and remnants of the columnar amorphous microstructure were found in the polycrystalline films. Complex impedance analyses revealed significant differences in dielectric behavior between the amorphous and crystalline films. Lumped circuit models were conducted on the films using resistors, capacitors, and constant phase elements. Amorphous films exhibited a single relaxation with Arrhenius activation energy of 1.1–1.3 eV. Crystallized films exhibited two relaxations with activation energies equal to 1.1 ± 0.08 and 0.6 ± 0.03 eV. The relative permittivity of the bulk crystalline grain in tantalum oxide films is close to the established permittivity of the β phase (er = 40) of Ta2O5.

The liquid source misted chemical deposition (LSMCD) method was employed in the preparation of lead zirconate titanate, Pb(Zr0.52Ti0.48)O3 (PZT) thin films. The desired thickness of the films was a...

Ferroelectric polarization switching of high aspect ratio (80:1) PbZr(0.52)Ti(0.48)O(3) (PZT) microtubes with a wall thickness of ~200 nm was investigated. A charge-based technique was used to assess the dielectric and ferroelectric properties of individual mechanically-unconstrained PZT microtubes with interdigitated electrodes. An enhancement in the degree of ferroelastic (non-180 degrees ) domain wall motion was observed in the tubes relative to films of similar thickness on rigid substrates. The dielectric response of the tubes showed a Rayleigh-like ac field dependence over a wide temperature range; the extent of the extrinsic contribution to the dielectric response dropped as the temperature approached 10K, but remained finite. This work demonstrates a general methodology for directly electrically addressing small, unconstrained ferroelectric devices, extending the range of driving fields and temperatures over which these materials can be probed.

The electrical properties of the fresnoite BaO–TiO2–SiO2 system were studied over a range of amorphous and crystalline microstructures using as-quenched glass (BTS-gl), partially crystallized glass (BTS-pc, heat treated at 740°C for 100 min) and fully crystallized glass ceramic (BTS-gc, heat treated at 750°C for 180 min). Combination of impedance and moduli plots along with equivalent circuit models were utilized in an attempt to understand the contributions arising from different regions in the glass ceramic, i.e. the glassy matrix, crystalline phase, and crystal–glass interface region. Electrical conductivity of the samples exhibited frequency dispersions at different temperatures suggesting localized motion of ions. The activation energies calculated from dc resistivity–temperature plots (Edc) and relaxation frequency–temperature plots (Ef) seem to increase as the degree of crystallinity increases suggesting that ionic transport becomes more difficult in crystallized glasses.

Vanadium oxide (VOx) thin films were deposited by reactive pulse dc magnetron sputtering process using a pure vanadium metal target. The structural, microstructure, and electrical properties were correlated as a function of processing parameters such as substrate temperature, Ar:O partial pressures ratios, and pulsed dc power to fabricate these films. The VOx films deposited at various substrate temperatures between 30 and 300°C using a range of oxygen to argon partial pressure ratios exhibited huge variation in their microstructure even though most of them are amorphous to x-ray diffraction technique. In addition, the electrical properties such as temperature coefficient of resistance (TCR), resistivity, and noise levels were influenced by film microstructure. The TCRs of the VOx films were in the range of −1.1%to−2.4%K−1 having resistivity values of 0.1–100Ωcm. In particular, films grown at lower substrate temperatures with higher oxygen partial pressures have shown finer columnar grain structure and ex...

The use of PZT films in sliver-mode high-frequency ultrasonic transducers applications requires thick, dense, and crack-free films with excellent piezoelectric and dielectric properties. In this work, PZT composite solutions were used to deposit PZT films >10 μm in thickness. It was found that the functional properties depend strongly on the mass ratio of PZT sol-gel solution to PZT powder in the composite solution. Both the remanent polarization, P(r), and transverse piezoelectric coefficient, e(31,) (f), increase with increasing proportion of the sol-gel solution in the precursor. Films prepared using a solution-to-powder mass ratio of 0.5 have a remanent polarization of 8 μC/cm(2), a dielectric constant of 450 (at 1 kHz), and e(31,) (f) = -2.8 C/m(2). Increasing the solution-to-powder mass ratio to 6, the films were found to have remanent polarizations as large as 37 μC/cm(2), a dielectric constant of 1250 (at 1 kHz) and e(31,) (f) = -5.8 C/m(2).

A KrF pulsed excimer laser (248 nm) was utilized to crystallize sputtered La-modified Pb(Zr,Ti)O3 (3:30:70) (PLZT) films on LaNiO3-coated silicon substrates. The film surface was irradiated with defocused laser pulses in an oxygen ambient at various substrate temperatures. Polycrystalline, phase pure perovskite PLZT thin films were produced for substrate temperatures of 250°C and higher. The dielectric constant and loss tangent values of laser-assisted crystallized (10 min exposure at 10 Hz using a substrate temperature of 400°C) PLZT thin films at 10 kHz were 406 and 0.027; in comparison, rapid thermal annealed films (annealed at 700°C for 1 min) showed values of 400 and 0.021, respectively. Laser crystallized films exhibited a remanent polarization value of 14 μC/cm2 with a coercive field |(E+c+E−c)|/2 of 95 kV/cm.

Dielectric and DC electrical properties of antiferroelectric lead zirconate and La-doped lead zirconate thin films deposited using a pulsed excimer-laser ablation technique were studied in detail. Increased La dopant concentration in pure lead zirconate thin films reduced the dielectric maximum and Curie temperature. At 9 mol.% of La in pure lead zirconate, the dielectric transition temperature reduced to room temperature. A gradual change from antiferroelectric to paraelectric through ferroelectric phases was observed with the addition of La to pure lead zirconate. The DC electrical properties of pure lead zirconate and the effect of donor addition on leakage current properties were studied. Correlation between the macroscopic changes observed in the charge transport mechanisms, microscopic defect chemistry and charge-carrier trapping phenomenon was examined in detail.

The mechanism of field induced phase switching in antiferroelectric lead zirconate and La-modified lead zirconate thin films has been analysed in terms of reversible and irreversible switching process under weak fields as a function of donor concentration. Extension of Rayleigh law of ferromagnetic materials to the present antiferroelectric and modified antiferroelectric compositions have clearly showed that origin of small signal dielectric permittivity is due to reversible domain wall motion. Rayleigh's constant, a measure of irreversible switching process, exhibited a slight increase with lower La3+ concentrations and followed by a gradual fall for higher concentration. This clearly illustrates that donor addition to antiferroelectric thin films controls the domain switching even under weak fields.

Lead zirconate is a room temperature antiferroelectric material, which exhibits double polarization hysteresis characteristic in the presence of external field. A transformation from antiferroelectric to paraelectric behavior through a ferroelectric phase has been exhibited upon addition of La-to pure lead zirconate thin films, which were confirmed from dielectric, hysteresis and pyroelectric and micro Raman analyses. Thin films of pure and La-modified lead zirconate were processed using A-site vacancy formula $Pb_{(1 - 1.5x)}La_XZrO_3$ by pulsed excimer laser ablation technique. Pyroelectric coefficient increased gradually from 55 to 190 $\mu C cm^ - ^2 K^ - ^ 1$ with the addition of 0 to 9 mole% of La to pure lead zirconate. The transition temperature has been reduced to room temperature ($\sim$34 °C) with addition of a 9 mole% of La-to lead zirconate. Presence of antiferroelectricity in pure lead zirconate thin films is due to antiparallel shifts of Pb-ions in (110) direction and reduction of transition temperature is attributed to creation of A-site vacancies would have caused enhancing of ferro-and paraelectric behavior with La-addition.

Thin films of neodymium-modified bismuth titanate Bi3.44Nd0.56Ti3O12 (BNT) were grown on Pt/TiO2/SiO2/Si substrates using chemical solution deposition method. The capacitors made by applying top Au electrodes on BNT films showed significantly improved values of the remanent polarization as compared to that using bismuth titanate Bi4Ti3O12 (BT) films. The 2P(r) value for the BNT capacitors was determined to be equal to 38 muC/cm(2) at an applied voltage of 24 V, whereas, for Bi4Ti3O12 ( BT) capacitors a value of 20 muC/cm(2) was measured at the same applied voltage. The maximum piezoelectric and pyroelectric coefficients of 22 pm/V and 112 muC/m(2) K respectively, were measured for the BNT thin films.

Antiferroelectric lead zirconate (PZ) thin films were deposited by excimer laser ablation technique on Pt-coated Si substrates. Antiferroelectric thin film compositions are potential candidates for high charge storage and microelectromechanical systems. The antiferroelectric nature in PZ thin films was confirmed by means of double hysteresis behaviour in polarisation vs. applied electric field and double butterfly response in capacitance vs. applied voltage measurements. The maximum spontaneous polarisation observed was $37 \mu C/cm^2$ with zero remnant polarisation at an applied electric field of 225 kV/cm. PZ thin films showed a polycrystalline multigrain structure and detail comprehensive study of dielectric relaxation and ac electrical properties were carried out.

Paraelectric lanthanum doped lead titanate (PLT) thin films for high permittivity material applications were grown on Pt-coated Si-substrates by the laser ablation technique. A rapid thermal annealing (RTA) process was adopted to induce crystallization and a polycrystalline fine microstructure was obtained. The dielectric properties, capacitance–voltage (C–V) characteristics and polarization hysteresis (P–E) with temperature were studied. The dielectric constant was approximately 720 while the dissipation factor was approximately 0.04 at room temperature for a 0.9-μm thick film at 100 kHz frequency. Hysteresis behavior was observed in C–V and P–E responses and was attributed to the presence of charge accumulation either in the grain boundaries or in the electrode–film interface. The charge storage density aspect was studied for DRAM applications and the obtained charge storage density at 6 V was 4.5 μC/cm2. The density of surface charge states was approximately 1013 cm2/eV at room temperature and the effect of temperature and frequency was studied and correlated with the properties of the film.

Antiferroelectric materials (example: lead zirconate and modified lead zirconate stannate), in which a field-induced ferroelectric phase transition is feasible due to a small free energy difference between the ferroelectric and the antiferroelectric phases, are proven to be very good candidates for applications involving actuation and high charge storage devices. The property of reverse switching from the field-induced ferroelectric to antiferroelectric phases is studied as a function of temperature, applied electric field, and sample thickness in antiferroelectric lead zirconate thin films deposited by pulsed excimer laser ablation. The maximum released charge density was 22 μC/cm2 from a stored charge density of 36 μC/cm2 in a 0.55 μ thick lead zirconate thin film. This indicated that more than 60% of the stored charge could be released in less than 7 ns at room temperature for a field of 200 kV/cm. The content of net released charge was found to increase with increasing field strength, whereas with increasing temperature the released charge was found to decrease. Thickness-dependent studies on lead zirconate thin films showed that size effects relating to extrinsic and intrinsic pinning mechanisms controlled the released and induced charges through the intrinsic switching time. These results proved that antiferroelectric PZ thin films could be utilized in high-speed charge decoupling capacitors in microelectronics applications.

Utilization of antiferroelectric thin films was proposed for high charge storage capacitors and transducer applications. The volume changes that are associated with the AFE⇒ FE and FE ⇒ AFE phases are high enough to use them in MEMs device technology. Lead zirconate was the first identified antiferroelectric compound with a reported dielectric phase transition temperature of ∼ 230°C. In this article, deposition of lead zirconate thin films by a pulsed excimer laser ablation technique is reported. The antiferroelectric nature of the lead zirconate thin films were confirmed by the presence of double hysteresis loop in polarization vs. applied electric field response as well as double butterfly behavior in capacitance vs. voltage characteristics. The variations in the polarization hysteresis with temperature were elucidated in detail. The switching times between the field induced FE and AFE phases (backward switching) were studied at various applied electric fields.

Antiferroelectric compositions have many potential applications in energy conversion and microelectromechanical systems. Electric field induced phase transitions between ferroelectric and antiferroelectric phases were studied in antiferroelectric lead zirconate and modified lead zirconate titanate stannate family thin films for various smart system applications. Thin films of various antiferroelectric thin film compositions such as $PbZrO_3$, Nb- and La-modified lead zirconate titanate stannate were processed by the pulsed excimer laser ablation technique. Dielectric, hysteresis, pyroelectric and switching properties were studied in detail for a new generation of functional materials. A comparative study of functional properties is presented with these antiferroelectric compositions in comparison with the conventional ferroelectric compositions

Antiferroelectric materials are found to be good alternative material compositions for high charge storage devices and transducer applications. Lead zirconate (PZ) is a room temperature antiferroelectric material. Thin films of PZ with various thicknesses were deposited by excimer laser ablation technique on Pt coated Si-substrates at a substrate temperature of 300°C and,subsequently, post annealed at 650°C. The antiferroelectric nature of PZ thin films was studied over a temperature range 30–250°C. Effect of thickness on the net dielectric constant was studied in detail and the calculated interfacial dielectric layer thickness is 0.1 nm approximately, with a bulk dielectric constant of 222 at 100 kHz. Impedance and electric modulus formalisms were employed in order to gain an insight of the microstructural details of multigrain thin films. A comprehensive study on relaxation mechanism revealed that the Maxwell–Wagner type polarization is the basic relaxation phenomenon in the multigrain PZ thin films, due to the presence of multiple grain and grain boundaries across the film thickness. The activation energies from the interior grain relaxation and ac conductivity studies were 0.631 and 0.563 eV, respectively. These activation energies were attributed to the excitation of the charge carriers from a set of shallow traps and:or oxygen vacancies present at an average depth of 0.5–0.6 eV from the bottom of the conduction band.

The dielectric and electrical properties of excimer laser ablated processed paraelectric $(Ba_{0.5},Sr_{0.5})TiO_3$ ferroelectric Bi-layered $SrBi_2(Ta_{0.5}Nb_{0.5})_2O_9$ and antiferroelectric $(PbZrO_3)$ thin films have been investigated. The effect of processing parameters on the microstructure of the films and the functional properties has been presented in detail. Some of the recent studies of stress induced effects, dielectric, hysteresis and ac and dc electrical properties have been highlighted in conjunction with microstructures of the films

Antiferroelectric lead zirconate thin films were deposited using KrF (248 nm) excimer laser ablation technique. Utilization of antiferroelectric materials is proposed in high charge storage capacitors and microelectromechanical (MEMs) devices. The antiferroelectric nature of lead zirconate thin films was confirmed by the presence of double hysteresis behavior in polarization versus applied field response. By controlling the processing parameters, two types of microstructures evolved, namely columnar (or in-situ) and multi-grained (or ex-situ) in PZ thin films. The dielectric and electrical properties of the lead zirconate thin films were studied with respect to the processing parameters. Analysis on charge transport mechanism, using space charge limited conduction phenomenon, showed the presence of both shallow and deep trap sites in the PZ thin films. The estimated shallow trap energies were 0.448 and 0.491 eV for in-situ and ex-situ films, with respective concentrations of ≈7.9×10 18 /cc and ≈2.97×10 18 /cc. The deep trap energies with concentrations were 1.83 eV with 1.4×10 16 /cc for ex-situ and 1.76 eV with 3.8×10 16 /cc for in-situ PZ thin films, respectively. These activation energies were found to be consistent with the analysis from Arrhenius plots of dc current densities.

Antiferroelectric lead zirconate (PZ) thin films were deposited by pulsed laser ablation on platinum-coated silicon substrates. Films showed a polycrystalline pervoskite structure upon annealing at 650 °C for 5–10 min. Dielectric properties were investigated as a function of temperature and frequency. The dielectric constant of PZ films was 220 at 100 kHz with a dissipation factor of 0.03. The electric field induced transformation from the antiferroelectric phase to the ferroelectric phase was observed through the polarization change, using a Sawyer–Tower circuit. The maximum polarization value obtained was 40 μC/cm2. The average fields to excite the ferroelectric state, and to reverse to the antiferroelectric state were 71 and 140 kV/cm, respectively. The field induced switching was also observed through double maxima in capacitance–voltage characteristics. Leakage current was studied in terms of current versus time and current versus voltage measurements. A leakage current density of 5×10−7 A/cm2 at 3 V...

Utilization of antiferroelectric thin films was proposed for high charge storage capacitors and transducer applications. The volume changes that are associated with the AFE [right double arrow] FE and FE [right double arrow] AFE phases are high enough to use them in MEMs device technology. Lead zirconate was the first identified antiferroelectric compound with a reported dielectric phase transition temperature of [similar to] 230°C. In this article, deposition of lead zirconate thin films by a pulsed excimer laser ablation technique is reported. The antiferroelectric nature of the lead zirconate thin films were confirmed by the presence of double hysteresis loop in polarization vs. applied electric field response as well as double butterfly behavior in capacitance vs. voltage characteristics. The variations in the polarization hysteresis with temperature were elucidated in detail. The switching times between the field induced FE and AFE phases (backward switching) were studied at various applied electric fields

Excimer laser assisted re-oxidation for reduced, crystallized BaTiO3 thin films on Ni-foils was investigated. It was found that the BaTiO3 can be re-oxidized at an oxygen partial pressure of ∼50 mTorr and substrate temperature of 350 °C without forming a NiOx interface layer between the film and base metal foil. The dielectric permittivity of re-oxidized films was >1000 with loss tangent values

Microelectromechanical systems (MEMS) incorporating active piezoelectric layers offer integrated actuation, sensing, and transduction. The broad implementation of such active MEMS has long been constrained by the inability to integrate materials with giant piezoelectric response, such as Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PMN-PT). We synthesized high-quality PMN-PT epitaxial thin films on vicinal (001) Si wafers with the use of an epitaxial (001) SrTiO(3) template layer with superior piezoelectric coefficients (e(31,f) = -27 ± 3 coulombs per square meter) and figures of merit for piezoelectric energy-harvesting systems. We have incorporated these heterostructures into microcantilevers that are actuated with extremely low drive voltage due to thin-film piezoelectric properties that rival bulk PMN-PT single crystals. These epitaxial heterostructures exhibit very large electromechanical coupling for ultrasound medical imaging, microfluidic control, mechanical sensing, and energy harvesting.

Uncooled Infrared (IR) focal plane arrays are an enabling technology for both military and commercial high sensitivity night vision cameras. IR imaging is accomplished using MEMS microbolometers fabricated on read-out integrated circuits and depends critically on the material used to absorb the incoming IR radiation. Suitable detector materials must exhibit a large temperature coefficient of resistance (TCR) and low noise characteristics to efficiently detect IR photons while also maintaining compatibility with standard integrated circuit (IC) processing. The most commonly used material in uncooled infrared imaging detectors is vanadium oxide deposited by reactive ion beam sputtering. Here we present a comparison of vanadium oxide thin films grown via commercial reactive ion beam sputtering to films grown using reactive pulsed DC magnetron sputtering. Films deposited using both methods were optically and structurally characterized using Raman spectroscopy, transmission electron microscopy, atomic force microscopy and grazing incidence X-ray diffraction. The measured electrical properties of the films were found to be very sensitive to the deposition conditions used. The ion beam sputtered films contained twinned FCC VOx nanocrystals with sub-nanometer twin spacing, in the form of large 10-20 nm wide columnar/conical grains. In contrast, the un-biased magnetron sputtered films consisted of equiax grains of FCC VOx (5-10 nm) encapsulated in an amorphous matrix. However, applying an RF bias to the sample substrate during the magnetron sputtering process, resulted in films that are similar in structure to ion beam deposited VOx. These differences in microstructure and composition were then correlated to the measured resistivities and TCRs of the films.

Reactive pulsed DC sputtering was used to grow a systematic series of films with resistivity ranging from 1 × 10-3 to 6.8 × 104 Ohm cm and TCR varying from 0 to -4% K-1. Throughout the parameter space studied a transition from amorphous to nano-crystalline growth was observed. Films in the resistivity range of interest for microbolometers contained a FCC VOx (0.8 < x < 1.3) phase. Altering the sputtering energetics via substrate biasing resulted in highlycolumnar, nano-twinned grains of FCC VOx, providing a microstructure reminiscent of ion beam sputtered bolometer material. Electron diffraction in the TEM confirmed the presence of a secondary, oxygen-rich amorphous phase. Micro- Raman spectroscopy, which was also found to be sensitive to the secondary amorphous phase, was used to probe the chemical composition and morphology of VOx thin films. Raman spectra from high resistivity amorphous films show a broad feature around ~890 cm-1, while spectra from lower resistivity nano-crystalline films exhibit this same amorphous feature and a second broad feature at ~320 cm-1. The resulting microstructure can be described as a nano-composite material composed of a low-resistivity crystalline phase embedded in a high-resistivity amorphous matrix. Our results suggest that both phases are required to achieve a high TCR, low resistivity material.

The dielectric and ferroelectric switching properties of high temperature\penalty1000-\hskip0pthigh energy density (1\ensuremath{-}$x$)BaTiO${}_{3}$-$x$BiScO${}_{3}$ ($0.1\ensuremath{\leqslant}x\ensuremath{\leqslant}0.4$) dielectrics were investigated over a broad temperature range. It was found that these ceramics possess dipole glass features such as critical slowing down of the dielectric relaxation, polarization hysteresis aging, rejuvenation, and holelike memory below the dipole glass transition temperature (${T}_{\mathrm{DG}}$). The dielectric relaxation behavior is consistent with a three-dimensional Ising model with critical slowing exponents $(z\ensuremath{\upsilon})=10\ifmmode\pm\else\textpm\fi{}1$ and composition-dependent glass transition temperatures. At lower temperatures, (1\ensuremath{-}$x$)BaTiO${}_{3}$-$x$BiScO${}_{3}$ ceramics transform into a reentrant dipole glass state owing to the breakup of local polar ordering. A phase diagram is developed marking the paraelectric, ferroelectric, and dipole glass regimes as a function of composition with the reentrant features.

Antiferroelectric materials are found to be good alternative material compositions for high-charge-storage devices and transducer applications. Lead zirconate (PZ) is a room-temperature antiferroelectric material. The antiferroelectric nature of PZ thin films was studied over a temperature range of 24-300°C, in terms of Raman scattering, dielectric constant, and polarization. Temperature-dependent dielectric and polarization studies indicated a nonabrupt phase transition. To alleviate the extrinsic effects influencing the phase transition behavior, Raman scattering studies were done on laser-ablated PZ thin films as a function of temperature and clear phase transformations were observed.

Niobium-modified lead zirconate stannate titanate antiferroelectric thin films with the chemical composition of (Pb0.99Nb0.02)(Zr0.57Sn0.38Ti0.05)0.98O3 were deposited by pulsed excimer laser ablation technique on Pt-coated Si substrates. Field-induced phase transition from antiferroelectric to ferroelectric properties was studied at different fields as a function of temperature. The field forced ferroelectric phase transition was elucidated by the presence of double-polarization hysteresis and double-butterfly characteristics from polarization versus applied electric field and capacitance and voltage measurements, respectively. The measured forward and reverse switching fields were 25 kV/cm and 77 kV/cm, respectively. The measured dielectric constant and dissipation factor were 540 and 0.001 at 100 kHz, respectively, at room temperature.

Polycrystalline films of SrBi2Nb2O9 were grown using pulsed-laser ablation. The ferroelectric properties were achieved by low-temperature deposition followed by a subsequent annealing process. The lower switching voltage was obtained by lowering the thickness, which did not affect the insulating nature of the films. The hysteresis results showed an excellent square-shaped loop with results (Pr = 6 μC/cm2, Ec = 100 kV/cm) in good agreement with earlier reports. The films also exhibited a dielectric constant of 250 and a dissipation factor of 0.02. The transport studies indicated an ohmic behavior, while higher voltages induced a bulk space charge.

High aspect ratio (< 30:1) ferroelectric structures have potential applications in areas such as tunable photonic crystals, biosensors and miniaturized transducers. Mechanically unconstrained and free standing Pb(Zr0.52,Ti0.48)O3 (PZT) tubes (1?2 microns in diameter) were processed with pre-patterned porous silicon templates using a Liquid Source Misted Chemical Deposition (LSMCD) technique. After pyrolysis at 300 °C for 2 min, these arrays were released using a combination of reactive ion etching and a XeF2 silicon etch methods. Surface contamination on these tubes was dissolved with a mild (0.1 M) boric acid treatment prior to rapid thermal crystallization (750 °C for 1 min). Pervoskite phase formation was confirmed by X-ray diffraction. Small signal electrical properties on a single PZT tube were measured using a set of interdigitated electrodes. The measured capacitance was 7 fF with 5 % loss. The ferroelectric switching was confirmed with capacitance ! vs. dc bias response with a coercive voltage of 8 V. The temperature dependent nonlinear dielectric response in these free standing structures were quantified using Rayleigh analysis down to 10 K. A comparison between PZT thin films and tube of similar wall thickness was made. These measurements suggest that domain wall contributions in thin films are limited by substrate clamping, whereas mechanically unconstrained tube structures have higher extrinsic domain wall contribution to the dielectric and piezoelectric properties.

Highly oriented and polycrystalline zirconium titanate thin films were deposited onto a p-type silicon substrate using laser ablation technique. Capacitance–voltage characteristics of metal-oxide semiconductor (MOS) capacitors were investigated in the temperature range between room temperature and 250°C for both the polycrystalline and highly oriented zirconium titanate thin films. The high frequency C–V curve has been measured at room temperature. There is a transition to low frequency C–V curve on supplying thermal energy to the MOS capacitor. A plot of the transition frequency versus reciprocal temperature shows an activation energy of $n_i$, which is dependent on the temperature and is equal to half of the silicon band gap energy. This indicates that the dominating mechanism is the generation–recombination of the minority carriers in the space charge region, related to bulk traps of silicon.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

A pulsed laser deposition system with in situ laser annealing was utilized to grow Pb(Zr0.52Ti0.48)O3 thin films on a laser crystallized Pb(Zr0.20Ti0.80)O3 seed layer, at a temperature of ∼370 °C. Polycrystalline 1.1 μm thick films exhibited columnar grains with small grain sizes (∼30 nm). The films showed well-saturated hysteresis loops (with ∼25 μC/cm2 remanent polarization, ∼50 kV/cm coercive field) and exhibited loss tangents

Dielectrics that provide higher electrostatic energy densities are urgently required for power electronic applications; recent observations in the solid solution of (1 − x)BaTiO3 − xBiScO3 show promise, and low temperature re-entrant dipole glass behavior is inferred. Here, direct observations of switchable polarization freezing in the reentrant dipole-glass (1 − x)BaTiO3 − xBiScO3, 0.1 ≤ x ≤ 0.4 are reported. As the temperature is decreased, the switchable polarization increases rapidly, reaches a maximum value at the reentrant temperature (TR) before disappearing at low temperatures. With measurement electric field (E), the TR is found to increase in (1 − x)BaTiO3 − xBiScO3, 0.1 ≤ x ≤ 0.4, as a function of x.

Cathode hysteresis in the reactive pulsed dc sputtering of a vanadium metal target was investigated to correlate the structural and electrical properties of the resultant vanadium oxide thin films within the framework of Berg’s model [Berg et al., J. Vac. Sci. Technol. A 5, 202 (1987)]. The process hysteresis during reactive pulsed dc sputtering of a vanadium metal target was monitored by measuring the cathode (target) current under different total gas flow rates and oxygen-to-argon ratios for a power density of ∼6.6.W/cm2. Approximately 20%–25% hysteretic change in the cathode current was noticed between the metallic and oxidized states of the V-metal target. The extent of the hysteresis varied with changes in the mass flow of oxygen as predicted by Berg’s model. The corresponding microstructure of the films changed from columnar to equiaxed grain structure with increased oxygen flow rates. Micro-Raman spectroscopy indicates subtle changes in the film structure as a function of processing conditions. The...

RF sputtered amorphous Pb(Zr0.52Ti0.48)O3 (PZT) films (∼300–350 nm in thickness) on {111}Pt/Ti/SiO2/Si or {001}PbTiO3/Pt/Ti/SiO2/Si substrates were laser crystallized to obtain highly textured {111} and {001} PZT thin films. The measured remanent polarizations and coercive fields were 31 µC/cm2 and 86 kV/cm for {001} films and 24 µC/cm2 and 64 kV/cm for {111} oriented PZT films, respectively. The maximum e31,f piezoelectric charge coefficients are ∼ −11 C/m2 for {001} and ∼ −9 C/m2 for {111} PZT thin films respectively.

Dielectric and piezoelectric properties of morphotropic phase boundary (Bi,Na)TiO3–(Bi,K)TiO3–BaTiO3 epitaxial thin films deposited on SrRuO3 coated SrTiO3 substrates were reported. Thin films of 350 nm thickness exhibited small signal dielectric permittivity and loss tangent values of 750 and 0.15, respectively, at 1 kHz. Ferroelectric hysteresis measurements indicated a remanent polarization value of 30 μC/cm2 with a coercive field of 85–100 kV/cm. The thin film transverse piezoelectric coefficient (e31,f) of these films after poling at 600 kV/cm was found to be −2.2 C/m2. The results indicate that these BNT-based thin films are a potential candidate for lead-free piezoelectric devices.

Low temperature charge transport in vanadium oxide (VOx) thin films processed using pulsed dc sputtering is investigated to understand the correlation between the processing conditions and electrical properties. It is identified that the temperature dependent resistivity ρ(T) of the VOx thin films is dominated by a Efros–Shklovskii variable range hopping mechanism [Efros and Shklovskii, J. Phys. C 8, L49 (1975)]. A detailed analysis in terms of charge hopping parameters in the low temperature regime is used to correlate film properties with the pulsed dc sputtering conditions.

Vanadium oxide (VOx) thin films were deposited on thermally grown silicon oxide substrates using a pure vanadium target in a pulsed dc sputtering technique. Film microstructure, electrical resistivity, temperature coefficient of resistance (TCR) and activation energy were studied as a function of the oxygen partial pressure (pO2) and growth temperatures. The mixed valence VOx thin films deposited at various substrate temperatures between 40 and 300 °C exhibited columnar grain structure even though the samples were found to be x-ray amorphous. The TCR and activation energies of the films increased from 0.4% (K−1) to 2.4% (K−1) and 0.04 eV to 0.28 eV, respectively, by controlling the pO2 content between depositions. The charge carrier transport in the VOx thin films was found to exhibit conventional and inverse Meyer–Neldel compensation mechanisms depending on the growth conditions.

The nonlinear dielectric response in [001] and [111] (1−x)Pb(Zn1∕3Nb2∕3)O3-xPbTiO3 (x=0.045 and 0.08) single crystals was investigated as a function of frequency between 30 and 250 °C. For comparison, a parallel study was carried out on a BaTiO3 single crystal. Both second and third harmonic polarization components were detected in Pb(Zn1∕3Nb2∕3)O3-PbTiO3 and BaTiO3 single crystals, and were observed to go through maxima at the phase transition temperatures. The third harmonic signal was nearly frequency independent for BaTiO3, but strongly dispersive in Pb(Zn1∕3Nb2∕3)O3-PbTiO3. The strong frequency dependence appears to be characteristic of some relaxor substructure of the domains.

(00l) epitaxial AgTaO3 and AgNbO3 thin films were prepared on (001)SrRuO3∕(001)LaAlO3 substrates by chemical solution deposition. The dielectric constants and loss of ∼300nm thick films were 110±10 and 0.025±0.005 for AgTaO3 and 550±55 and 0.020±0.005 for AgNbO3 at room temperature. In both films, the temperature coefficient of capacitance is smaller than that for bulk ceramics of the same composition. The capacitance changes from −20to120°C were ⩽1.2% for AgTaO3 and ⩽3.6% for AgNbO3. The tunability of the AgTaO3 film was 1.6% at 230kV∕cm field, while 21% tunability was measured for AgNbO3 at 190kV∕cm.

By combining optical lithography and chemical self-assembly, the authors circumvent the limitations of photolithography and provide a parallel, low-cost alternative to fabricate sub-50nm features. Self-assembled multilayers, composed of alternating layers of α,ω-mercaptoalkanoic acids and copper (II) ions (“molecular rulers”), are used as an organic sidewall spacer resist on initial lithographic structures enabling the precise, proximal placement of a secondary structure via lift-off. Here, the authors implemented a positive-tone bilayer resist for improved line-edge characteristics of the secondary structure and evaluated the lithographic and electrical performance of nanostructures fabricated using this approach. Additionally, they describe extensions of this technique by which planar nanojunctions were created, and the generated nanometer-scale pattern was transferred to the underlying substrate.

Bi-layered Aurivillius compounds prove to be efficient candidates of nonvolatile memories.$SrBi_2Nb_2O_9$ thin films were deposited by excimer laser ablation at low substrate temperature (400°C) followed by an ex situ annealing at 750 °C. The polarization hysteresis behavior was confirmed by variation of polarization with the external applied electric field and also verified with capacitance versus voltage characteristics. The measured values of spontaneous and remnant polarizations were, respectively, 9 and 6 $\mu$C/cm2 with a coercive field of 90 kV/cm. The measured dielectric constant and dissipation factors at 100 kHz were 220 and 0.02, respectively. The frequency analysis of dielectric and ac conduction properties showed a distribution of relaxation times due to the presence of multiple grain boundaries in the films. The values of activation energies from the dissipation factor and grain interior resistance were found to be 0.9 and 1.3 eV, respectively. The deviation in these values was attributed to the energetic conditions of the grain boundaries and bulk grains. The macroscopic relaxation phenomenon is controlled by the higher resistive component in a film, such as grain boundaries at lower temperatures, which was highlighted in the present article in close relation to interior grain relaxation and conduction properties.

A phenomenological approach is proposed describing both nonlinearity and frequency dispersion in dielectric and piezoelectric properties of lead zirconate titanate, Pb(Zr,Ti)O-3 (PZT), thin films and ceramics. The approach couples the frequency dependent response in form of the power law, 1/omega(beta), with the rate-independent nonlinear response described by the Rayleigh law. The main experimental trends are well described by the model. (c) 2005 Elsevier B.V. All rights reserved.