bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and Electrical Investigations of Ferroelectric Lead Strontium Titanate Thin Films and Ceramics
Authors: Jain M. , Bhattacharya P. , Yuzyuk Yu. I. , Katiyar R. S. , Bhalla A. S. 
Published: April 2011

ABSTRACTLead strontium titanate (PbxSr1-xTiO3) (x=0.3–1.0) ceramic targets were prepared by the conventional powder-processing method. Thin films of these compositions were deposited on platinized silicon substrates by pulsed laser deposition technique. X-ray diffraction studies of the ceramic targets showed that the lattice structure changes from tetragonal to cubic phase with the increase of Sr content in PbTiO3. Raman spectroscopic studies of PbxSr1-xTiO3(PST) ceramics and thin films showed that the soft mode decreases to lower frequency and finally disappear at around 60–70 at% Sr content, which confirms the tetragonal to cubic phase transition at room temperature. Dielectric constant measured for PST thin films was in the range of 900–1500 at 1 MHz, with maximum value obtained for PST30 thin film. The loss tangents at room temperature were in the range of 0.07–0.1 for PST thin films with different compositions.
Mist Deposition of Micron-Thick Lead Zirconate Titanate Films
Authors: Losego Mark D. , Trolier-McKinstry Susan 
Published: April 2011

ABSTRACTA majority of the work published on liquid source misted chemical deposition (LSMCD) has focused on the fabrication of thin ferroelectric films for random access memory (RAM) applications. However, the ability of LSMCD to combine the characteristically good stoichiometry control of a chemical solution deposition process with good film conformality, makes this a desirable technique for other applications, including microactuators and integrated passive components. For these applications, though, LSMCD is limited by its low throughput. This paper describes the feasibility of depositing micron-thick lead zirconate titanate (PZT) films using the LSMCD tool. PZT films of 52/48 composition were deposited on both platinized silicon and platinized alumina substrates. The chamber temperature and the delivery geometry of the LSMCD tool were identified as limiting factors in the rate at which micron-thick samples can be prepared. By switching to a focused nozzle delivery geometry and increasing the chamber temperature from room temperature to 60°C, the total process time for 1 μm thick films can be reduced from 480 min to 90 min. Polarization hysteresis measurements indicated a 75% higher remanent polarization for PZT films deposited on platinized alumina substrates (35 μC/cm2) compared to those deposed on platinized silicon substrates (20 μC/cm2). The polarization loop for the silicon substrate sample was also tilted. These observations are evidence of higher tensile stresses in the PZT films deposited on silicon substrates due to a larger mismatch in the thermal expansion coefficients of the film and the substrate.
The Synthesis and Structure of New Perovskite-type Niobate Processed in Millimeter Wave Field
Authors: Liu Hanxing , Zou Long , Zhou Jian , Yuan Guangjiang , Hua Hua , Luo Dabing , Luo Jirun , Ouyang Shixi 
Published: April 2011

ABSTRACTIn present paper a new niobate materials Ba5LixTixNb10-xO30 were synthesized by doping Li+ in the system BaO- TiO2- Nb2O5 in millimeter wave field. X-ray diffraction (XRD) quantitative and scanning transition spectroscopy (SEM) analysis were employed to study crystal structure and microstructure of reaction products. It was found that pure products could be obtained at temperature 900°, 8 min which is lower comparing with that by conventional method. The XRD data shown the crystal belongs to tetragonal tungsten bronze structure with space group P4bm. The grain size synthesized in millimeter wave field had smaller size, narrower distribution, better sinter-ability, and without hard agglomeration comparing whit that obtaining from conventional synthesis. At lower temperature Ba5LiTiNb9O30 is a tetragonal ferroelectric phase.
Ir Thin Films for PZT Capacitors Prepared by MOCVD Using a New Ir Precursor
Authors: Fujisawa H. , Watari S. , Shimizu M. , Niu H. , Oshima N. 
Published: April 2011

ABSTRACTPreparation of Ir thin films for PZT capacitors by MOCVD using a new liquid Ir precursor, Ir(EtCp)(CHD) was investigated. Ir thin films with a highly reflecting surface and (111)-orientation were successfully obtained at 230–400 C. When Ir(EtCp)(CHD) was used, shorter incubation time (20min at 230°C and not observed above 240°C) and higher nucleation density (300–400mm-2at 250–300°C) were observed because of its lower decomposition temperature (300°C) than that of previously reported liquid precursor, Ir(EtCp)(COD). Resistivity of 100nm-thick Ir films grown at 250–350°C were less than 20μΩ·cm. PZT capacitors with top and bottom electrodes prepared using Ir(EtCp)(CHD) showed D-E hysteresis loop with Pr of 15μC/cm and Ec of 60kV/cm. No degradation of switching up to 10 switching cycles by bipolar pulses of ±231kV/cm (±3V) and 500kHz.
MOCVD of Ferroelectric Thin Films
Authors: Rice C. E. , Sun S. , Cuchiaro J. D. , Provost L. G. , Tompa G. S. 
Published: April 2011

ABSTRACTWe have examined the growth of a number of important ferroelectric oxides by MOCVD using a rotating disk reactor. Highly uniform and reproducible films over 6” wafers have been routinely achieved. Materials include Lead Zirconate Titanate (PZT, PbZrxTi1-xO3), Lead Lanthanum Zirconate Titanate (PLZT), Strontium Bismuth Tantalate (SBT), CeMnO3 (CMO), and others. Emphasis has been on achieving highly crystalline and oriented films at the lowest deposition temperatures possible, for compatibility with other integrated device materials and processing; and the achievement of optimum ferroelectric and pyroelectric performance. The effects of varying growth parameters, barrier and/or template layers, and post-growth annealing have been studied. The growth process, physical characterization, and ferroelectric film properties will be discussed.
Enhancement of Aurivillius Phase Formation Kinetics in SBT Thin Films using Nanoparticle Seeding
Authors: Sung Yun-Mo , Kwak Woo-Chul , Jung Se-Yon , Hwang Seung-Joon 
Published: April 2011

ABSTRACTPt/Ti/SiO2/Si substrates seeded by SBT nanoparticles (∼60–80 nm) were used to enhance the phase formation kinetics of Sr0.7Bi2.4Ta2O9 (SBT) thin films. The volume fractions of Aurivillius phase formation obtained through quantitative x-ray diffraction (Q-XRD) analyses showed highly enhanced kinetics in seeded SBT thin films. The Avrami exponents were determined as ∼1.4 and ∼0.9 for unseeded and seeded SBT films, respectively, which reveals different nucleation modes. By using Arrhenius–type plots the activation energy values for the phase transformation of unseeded and seeded SBT thin films were determined to be ∼264 and ∼168 kJ/mol, respectively. This gives a key reason to the enhanced kinetics in seeded films. Microstructural analyses on unseeded SBT thin films showed formation of randomly oriented needle-like crystals, while those on seeded ones showed formation of domains comprised of directionally grown worm-like crystals.
Residual Stress Effects in Ferroelectric Thin Films
Authors: Berfield T. A. , Sottos N. R. , Ong R. J. , Payne D. A. 
Published: April 2011

ABSTRACTRecent developments in soft lithographic patterning enable the integration of functional ceramic thin films on a chip, rather than by adding discrete components to the system. As integrated device applications push the characteristic length scale of materials smaller and smaller, surface and interface effects play an important role, producing significant scientific challenges to the characterization of mechanical properties, performance and reliability. In this paper, we investigate the complex roles of microstructure, interface effects and residual stresses on ferroelectric thin film performance. Pb(Zr0.53Ti0.47)O3 films ranging in thickness from 190 nm to 500 nm were deposited by a sequential build up of sol-gel derived thin layers onto platinized Si substrates. Residual stresses in the films after thermal processing were observed and calculated from laser reflectance measurements of wafer curvature. Field-induced displacements were then measured by interferometric methods for films with well-characterized residual stress states. Results indicate significant increases in film performance with a decrease in measured residual tensile stress.
High Pressure Deposition of Epitaxial PZT Thin Films on Sr(Nb)TiO3
Authors: Blanco O. , Heiras J. , Siqueiros J. M. , Martínez E. , Andrade E. 
Published: April 2011

ABSTRACTEpitaxial thin ferroelectric films of Pb(Zr0.53Ti0.47) (PZT) were successfully grown on Sr(Nb)TiO3(SNTO) single crystal substrates by high-pressure rf sputtering. Pure O2was used as working gas at a pressure above 1 Torr. Deposition temperature was varied from 550°C to 600°C. Under these conditions we were able to deposit films at a rate of 2.7 Å/min. Their crystalline properties, evaluated by Θ/2Θ, ω and φ scans, showed both in-plane and out of plane orientation. Film composition and film-substrate interface characteristics were studied by Rutherford Backscattering Spectroscopy (RBS). For RBS data the composition ratios for the films were calculated having obtained the expected values for a stoichiometric composition. A very thin diffusion layer of Pb at the film-substrate interface was also introduced. However, the deficiency in Pb, which is correlated to the presence of oxygen vacancies, is lower in our films produced at high O2 pressure than those reported for films produced by sputtering at lower pressures. The ferroelectric hysteresis loops measured in the Pt/PZT/SNTO heterostructures show good ferroelectric behavior with remanent polarizations of 12μ Ccm-2and coercive field of 50kVcm-1at 5V. The high-pressured technique representing a useful and capable method capable of obtainingin situepitaxial, fully oxygenated, pyrochlore-free ferroelectric thin film with high quality structural, compositional and dielectric properties, without post deposit treatment.
Liquid injection MOCVD and ALD studies of “single source” Sr-Nb and Sr-Ta precursors
Authors: Potter Richard J. , Marshall Paul A. , Roberts John L. , Jones Anthony C. , Chalker Paul R. , Vehkamäki Marko , Ritala Mikko , Leskelä Markku , Williams Paul A. , Davies Hywel O. , Tobin Neil L. , Smith Lesley M. 
Published: April 2011

ABSTRACTA range of “single source” Sr-Nb and Sr-Ta heterometal alkoxides precursors are investigated as potential sources for liquid injection MOCVD (metalorganic chemical vapour deposition) and ALD (atomic layer deposition) of SrBi2Ta2O9 (SBT) and SrBi2(TxNb1-x)2O9 (SBTN). These “single source” precursors are designed to alleviate the mis-match between conventional Sr and Ta or Sr and Nb sources. Strontium-tantalate and strontium-niobate thin films were deposited on silicon using the “single source” alkoxide precursors [Sr{Ta(OEt)5(dmae}2] and [Sr{Nb(OEt)5(dmae)}2] (dmae = OCH2CH2NMe2), and the optimum temperatures for deposition of stoichiometric SrTa2O6 and SrNb2O6 were determined. Separate ALD studies of [Sr{Ta(OEt)5(dmae)}2] and [Sr{Ta(OEt)5(mee)}2] (mee = OCH2CH2OMe) for the growth of strontium-tantalate were carried out to assess precursor suitability for this technique. Liquid injection MOCVD of Bi-oxide films using Bi(mmp)3 indicates similar decomposition behaviour to the Sr-Ta and Sr-Nb alkoxides, demonstrating its suitability as a complementary source of Bi for SBT, SBN and SBTN.
Fabrication and Electrical Characterization of Ba(1-x)SrxTiO3 Based Thin Films
Authors: Ngo E. , Nothwang W. D. , Hubbard C. , Cole M. W. , Chang W. , Kirchoffer S. W. , Pond J. M. 
Published: April 2011

ABSTRACTOver the past several years there has been a tremendous growth and development of thin film deposition technology in the electronics industry. Ferroelectric thin films have been recognized for their unique dielectric properties and appear to be desirable for tunable microwave device applications. Among the most promising candidates for such applications are Ba(1−x)SrxTiO3[BST] and BST-based thin films. In this work pure BST and acceptor doped BST-based thin films were fabricated on (100) MgO substrates via pulsed laser deposition [PLD]. X-ray diffraction (XRD) in conjunction with the atomic force microscope (AFM) were used to analyze the film crystalinity and surface morphology. The dielectric properties were characterized at both 100 kHz and 20 GHz. The MIM capacitor configuration was used to attain the dielectric properties at 100 kHz and the microwave measurements, S11 reflection parameters, were achieved via interdigitated capacitor design with Au/Ag top electrodes. The parallel resistor-capacitor models were used to determine the microwave capacitance and Q factors and the permittivity was calculated using a modified conformal-mapping partial-capacitance method using the dimension of the capacitors. Our results demonstrated that the low frequency and microwave frequency dielectric properties were strongly influenced by the film composition. Specifically, the Mg doping served to lower the dissipation factor, permittivity, and tunability of the BST based films at both frequencies. This work demonstrates that the BST based thin films possessed excellent microstructural, structural, and dielectric properties. The structure-process-property correlations of the pulsed laser deposited BST and acceptor doped BST-based thin films are discussed in detail.
Microwave Properties of Parallel Plate Capacitors based on (Ba,Sr)TiO3 Thin Films Grown on SiO2/Al2O3 Substrates
Authors: Koutsaroff I. P. , Bernacki T. , Zelner M. , Cervin-Lawry A. , Kassam A. , Woo P. , Woodward L. , Patel A. 
Published: April 2011

ABSTRACTBa0.7Sr0.3TiO3 (BST) single and quadruple layer capacitors with Pt electrodes were fabricated together on polycrystalline alumina substrates with a SiO2-based multicomponent amorphous buffer layer (SiO2/Al2O3). This paper presents the results of the characterization of these capacitors, to demonstrate their suitability for application as decoupling (high value) capacitors and as components in tunable RF applications (e.g., phase shifters and filters). BST films of different compositions, (Ba0.7Sr0.3)TiO3 and (Ba0.5Sr0.5)TiO3, were grown by metal-organic decomposition (MOD) and RF magnetron reactive sputtering. The capacitance density of 90–140 nm thick BST films was in the range of 20 to 70 fF/μm 2. Parallel plate capacitors with areas from 16 μm2 to 2.25 mm2 were fabricated using photolithography and ion milling techniques. For large capacitors (0.125 to 2.25 mm2), capacitance and tanδ were measured at low frequencies (1 KHz - 1 MHz) using an LCR meter. Smaller capacitors (16 μm2 to 3600 μm2) were additionally characterized in the frequency range of 50 MHz - 20 GHz. In such case, capacitance, tanδ and equivalent series resistance (ESR) were extracted from two port scattering parameters obtained using a vector network analyzer (VNA). The relationship between dielectric loss, tunability and calculated figure of merit vs. BST composition and deposition temperature was outlined. In addition, loss and ESR at high frequencies was investigated. The typical achieved leakage current density of sputtered BST films for 2.25 mm2 capacitors fabricated on SiO2/Al2O3 was 7.3×10-9 A/cm2 at 300 kV/cm (65 fF/μm2), about 2 times lower than for (Ba0.7Sr0.3)TiO3 films deposited by MOD (1.4×10-8 A/cm2 at 300 kV/cm, 34.5 fF/μm2). Furthermore, the tunability of (Ba0.7Sr0.3)TiO3 deposited by both methods on SiO2/Al2O3 was ∼60% at 350 kV/cm.
Synchrotron X-ray Microdiffraction Images of Polarization Switching in Epitaxial PZT Capacitors with Pt and SrRuO3 Top Electrodes
Authors: Do Dal-Hyun , Kim Dong Min , Eom Chang-Beom , Dufresne Eric M. , Isaacs Eric D. , Evans Paul G. 
Published: April 2011

ABSTRACTThe evolution of stored ferroelectric polarization in PZT thin film capacitors was imaged using synchrotron x-ray microdiffraction with a submicron-diameter focused incident x-ray beam. To form the capacitors, an epitaxial Pb(Zr,Ti)O3 (PZT) thin film was deposited on an epitaxially-grown conductive SrRuO3 (SRO) bottom electrode on a SrTiO3 (STO) (001) substrate. Polycrystalline SRO or Pt top electrodes were prepared by sputter deposition through a shadow mask and subsequent annealing. The intensity of x-ray reflections from the PZT film depended on the local ferroelectric polarization. With 10 keV x-rays, regions of opposite polarization differed in intensity by 26% in our PZT capacitor with an SRO top electrode. Devices with SRO electrodes showed just a 25% decrease in the remnant polarization after 107 switching cycles. In devices with Pt top electrodes, however, the switchable polarization decreased a by 70% after only 5×104 cycles.
Polarization Reversal Model and Prediction of Temperature-Dependent Switching of Ferroelectric Capacitors
Authors: Stolichnov Igor , Tagantsev Alexander K. , Setter Nava , Cross Jeffrey S. 
Published: April 2011

ABSTRACTTemperature dependent performance of ferroelectric non-volatile memories is an important issue, that impacts memory device reliability. In general, the device temperature strongly influences the speed of polarization reversal in ferroelectric capacitors. In particular, the switching speed decreases with the decreasing temperature, which may give rise to incomplete switching. In the present work, the recently proposed Nucleation-Limited Switching model for ferroelectric thin films is extended for description of the temperature dependence of the polarization reversal. The model is shown to be valid for the temperature range important for memory applications. This model enables quantitative prediction of the switching performance of ferroelectric capacitors at different temperatures based upon results obtained at room temperature. The temperature and voltage range where the proposed concept is applicable is discussed in context of limits of validity of the Nucleation-Limited Switching model.
Low Voltage Operation of PZT Ferroelectric Film deposited by Liquid Source MOCVD
Authors: Nishioka Yutaka , Masuda Takeshi , Kajinuma Masahiko , Yamada Takakazu , Uematsu Masaki , Suu Koukou 
Published: April 2011

ABSTRACTThin Pb(Zr, Ti)O3 films were grown on a 8-inch Ir(111)/SiO2/Si substrate by a liquid-source MOCVD system. These films showed dependency of ferroelectric properties on several deposition parameters. PZT single phase was obtained at a substrate temperature of 620°C. The film showed (111) preferred orientation and the Pt/Pb1.16(Zr0.45, Ti0.55)Ox(115nm)/Ir capacitors had excellent ferroelectric properties. The switching charge (Qsw) value (at 2V), saturation voltage (V90) and leakage current density (at 1.5V) were 47.4uC/cm2, 1.7V and 7.5E-8A/cm2 respectively. The capacitor made by using an IrOx top electrode had excellent fatigue-free property.
Comparative studies on BaZrxTi1-xO3thin films deposited by Sol-gel and Pulse laser deposition
Authors: Dixit A. , Bhattacharaya P. , Majumder S. B. , Katiyar R. S. , Bhalla A. S. 
Published: April 2011

ABSTRACTFerroelectric thin films of BaZrxTi1-xO3(BZT) were deposited on platinum (Pt) and platinized silicon (Pt/Si) substrates by sol-gel and pulse laser deposition technique respectively. The structure and preferred orientation of the films were examined by x-ray diffraction measurements. The phase formation of sol-gel derived BZT films were found to be at high temperature (1100°C) compare to the pulse laser deposited BZT films ∼ 700°C. Polycrystalline films were observed by both techniques. Ferroelectric nature of the films was confirmed by hysteresis and capacitance-voltage characteristics using platinum top electrodes. Dielectric constant as well as loss was found to decrease by increasing Zr contents. Surface morphology predicted smooth crack free surface.
Temperature Dependent Raman Scattering and Dielectric Permittivity Measurements of Pb1−x Srx TiO3 Films
Authors: Naik V. M. , Smith M. , Dai H. , Talagala P. , Naik R. , Auner G. W. , Mantese J. 
Published: April 2011

ABSTRACTPb1-x Srx TiO3 (x = 0 to 1.0) films of thickness ∼ 4 μ m have been prepared on sapphire and Pt substrates by metalorganic decomposition (MOD) method. X-ray diffraction results show that the films are polycrystalline with a perovskite tetragonal phase at room temperature for x < 0.5 and a cubic phase for x > 0.5. Room temperature Raman spectra show a systematic variation of lattice vibrational modes with x. The most notable changes in the Raman spectra with x are the decrease in the splitting of A1(3TO) and E(3TO) modes and the disappearance of E(3TO) mode at x ∼ 0.6. Although the x-ray diffraction peaks for films with x > 0.5 show a cubic phase at room temperature, the Raman spectra show the characteristic phonon modes of a tetragonal phase even at x = 0.7. The dielectric permittivity versus temperature measurements for films with x ≤ 0.7 show a broad dielectric anomaly corresponding to a diffuse ferroelectric to paraelectric phase transition. The phase transition temperature (Tc) values are consistently lower than the corresponding bulk ceramic alloys. Furthermore, Tc are also determined by monitoring the temperature dependence of the splitting between E(3TO) and A1(3TO) phonon modes in the Raman spectra of Pb1-x Srx TiO3 films for x ≤ 0.6. There has been good agreement between the two methods.
Highly Efficient Piezoelectric Actuators for Active Vibration Control
Authors: Colla Enrico L. , Suyal Ganesh , Gentil Sandrine , Setter Nava 
Published: April 2011

ABSTRACTAn high performance / inexpensive diskbender actuator was produced by combining efficient design and fabrication methods and a new technique to operate these actuators was developed and tested, which can enhance the displacement and force capabilities by almost a factor of 2 by using the same maximal driving voltage.The properties of these actuators are intermediate between those of standard bimorphs, used for very large displacements but providing rather small forces, and those of low voltage stack multilayers, which provide quite large forces but are generally heavier, larger and expensive for equivalent displacements. The absence of any external mechanical amplification mechanism and their geometry make these actuators particularly suitable for active vibration damping applications within buildings affected by perturbations of hundreds of μm or for noise control by emission of controlled sound in antiphase. The class of displacement/force, which can be obtained with suitably dimensioned actuators, provides sufficient high motion even for the lower audio frequency region (400–1500 Hz).In order to lower the driving voltages, multilayer diskbenders were also fabricated with the same technique. The number of layers does not influence the actuator displacement and force properties but the increased capacity of the actuator may require sophisticated driving amplifiers.