bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical Study of PbTiO3 Thin Films Grown by Sol-Gel Technique
Authors: Ching-Prado E. , Tao R.W. , Katiyar R.S. , Bhalla A.S. 
Published: April 2011

ABSTRACTThin films of PbTiO3 were prepared by sol-gel method on platinum-coated-Si and Al2O3 and annealed at 600°C. The annealing time of the films, deposited on Si, were 6 and 12 hours, respectively. Micro-Raman spectra show high background in the low frequency region and the bands are broader with respect to the single crystal work, which indicates the polycrystalline nature of the samples. The film annealed for 12 hours showed more pronounced peaks in the spectra when compared to the film annealed for 6 hours. Micro-Raman measurements on different spots in the film indicate that the PT film on platinum-coated silicon substrate is highly inhomogeneous. In the case of PT/Al2O3 such studies show a homogeneous film. The frequencies of most of the modes are decreased, which is associated to grains under stress. The nature of the stress is discussed. Although film stress may not be homogeneous, a stress value around 1.2 GPa is estimated from Raman data. XRD and SEM techniques were used for structural characterization.
Photoferroelectric Effects of Undoped and Extrinsic Ion-Doped PZT Thin Films
Authors: Li Li , Lin Chhiu-Tsu , Leung Martin S. , Adams Paul M. , Lipeles Russell A. 
Published: April 2011

ABSTRACTDeposition by aqueous acetate solution (DAAS) technique was used to synthesize undoped and 5 wt% Cr-, Mn-, Eu-, or Pr-doped Pb(Zr0.53Ti0.47O3 [PZT] thin films. The dopant was incorporated into PZT either in the precursor coating solution or via thermal diffusion into undoped PZT. X-ray diffraction shows that ion-doped PZT thin films on Pt<l 1 l>/Ti/SiO2/Si<100> (in particular, the Mn- and Eu- doped samples) display better crystallinity and smaller lattice parameters than those on sapphire substrates. The enhancement of photoconductivity at visible wavelengths measured by excitation photocurrent spectroscopy (EPS) goes as Cr-doped∼Mn-doped > Eu-doped ∼ Pr-doped. Only Mn-doped PZT perovskites have the band gap energy red-shifted to 360 nm from 330 nm. The space charge (or photovoltaic) field was estimated to be < 8 v when about 100 v was applied to ion-doped PZT thin films with 260 or 320 nm light. By using laser irradiation at selected wavelengths and switching the polarity of applied bias voltage, the expected changes in resistance (Ry) and remanent polarization (±Pr) states were observed in the P-E hysteresis loops. The possible applications of extrinsic ion-doped PZT thin films in optical memory devices are discussed.
Impact of A Ti Adhesion Layer on Pt/PZT/Pt Capacitors
Authors: Jones R.E. , Mamar P.D. , Dupuie J.L. , Kim J. , Moazzamp R. , Witowski J. , Kottke M.L. , Saha N.C. , Gregory R.B. 
Published: April 2011

ABSTRACTA five-factor, full-factorial experiment on process sensitivity of non-volatile polarization, Pnv for Pt/PZT/Pt capacitors shows the most dramatic factor is the use, or not, of a Ti adhesion layer for the bottom electrode. With the Ti layer, Pnv is generally lower and is sensitive to several factors and interactions involving the crystallization anneal, sol-gel synthesis, and Pt thickness and deposition temperature. A possible cause is Ti diffusion through the Pt as observed in Auger and XPS depth profiles of oxygen annealed Pt/Ti electrodes.
Layered Structure Oxides for Fatigue Free Ferroelectric Applications
Authors: Vijay Dilip P. , Desu Seshu B. , Nagata Masaya , Zhang Xubai , Chen Tze C. 
Published: April 2011

ABSTRACTSrBi2(TaxNb1−x)2O9 (SBTN) layered structure oxides have been investigated for possible fatigue free ferroelectric thin film applications. High quality stoichiometric thin films of these oxides have been fabricated, across the solid solution range, using the technique of pulsed laser ablation SBTN thin films with a composition close to x=0.4 showed excellent ferroelectric properties and no fatigue up to 1010 switching cycles. Typically, these films showed a 2Pr value of 22 μC/cm2, an Ec of 60 kV/cm and a resistivity close to 5 × 1012 Ω-cm. The ferroelectric properties of these films were found to depend on the orientation. Predominantly c-axis oriented films have been fabricated on MgO (100)/Pt (100) substrates. By comparison, the c-axis oriented films were found to exhibit similar Pr values but significantly lower Ec values (by 15 kV/cm) and a higher resistivity. The fatigue free behavior of these layered structure oxides has been ascribed to the absence of any volatile species in their sublattice exhibiting polarization (i.e., the perovskite-like units in the layered structure).
Epitaxial Pb(Zr0.40Ti0.60)O3/SrRuO3 and PbTiO3/SrRuO3 Multilayer Thin Films Prepared by MOCVD and Rf Sputtering
Authors: Foster C.M. , Csencsits R. , Baldo P.M. , Bai G.R. , Li Z. , Rehn L.E. , Wills L.A. , Hiskes R. , Dimos P. , Sinclair M.B. 
Published: April 2011

ABSTRACTEpitaxial SrRuO3 thin films were deposited by RF sputtering on SrTiO3 or MgO substrates for use as underlying electrodes. On these conductive substrates, epitaxial Pb(Zr0.35Ti0.65)O3 (PZT) and PbTiO3 (PT) thin films were deposited by metalorganic chemical vapor deposition (MOCVD). X-ray diffraction (XRD), RBS channeling (RBS), transmission electron microscopy (TEM) and optical waveguiding were used to characterize the phase, microstructure, defect structure, refractive index, and film thickness of the deposited films. The PZT and PT films were epitaxial and c-axis oriented. 90° domains, interfacial misfit dislocations and threading dislocations were the primary structural defects, and the films showed a 70% RBS channelling reduction. Hysteresis and dielectric measurements of epitaxial PZT ferroelectric capacitor structures formed using evaporated Ag or ITO glass top electrode showed: a remanent polarization of 46.2 μC/cm2 a coercive field of 54.9 kV/cm, a dielectric constant of 410, a bipolar resistivity of ∼5.8×109 ω-cm at a field of 275 kV/cm, and a breakdown strength of >400 kV/cm.
Ferroelectric (Pb,La)TiO3 Thin Films Prepared by Metalorganic Chemical Deposition
Authors: C. Z. , Kwak B.S. , Erbil A. 
Published: April 2011

ABSTRACTRecently, we reported results of an investigation of the preparation of highly textured (Pb1−xLax)TiO3 (PLT) thin films grown on Si(100) by metalorganic chemical deposition (MOCVD) [1]. In this paper, we discuss an extension of this work to the growth of PLT thin films on fused quartz substrates by the MOCVD technique. A series of PLT films with x between 0 and 0.32 were prepared. Characterization by x-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS) and Raman scattering has been performed on these ferroelectric thin films. XRD indicated the polycrystalline nature of the PLT films and the variation of their tetragonality. The film thickness and La composition were determined by RBS. Raman spectra, measured at 300 and 80 K, showed features of the PLT film and quartz substrate. By using a “difference Raman” technique, more PLT modes were shown. The variations of the PLT Raman modes with the La composition and the measurement temperature were studied. Related physical phenomena and problems are discussed.
The Characterization and Electrical Properties of DOPED PZT Thin Films Prepared by Sol-Gel Processing
Authors: Lee Wan In , Lee J.K. , Chung Elsub , Chung C.W. , Yoo I.K. , Desu Seshu B. 
Published: April 2011

ABSTRACTPZT (Zr/Ti = 53/47), PNZT (4% Nb doped PZT), PSZT (2% Sc doped PZT), and PSNZT (1% Sc and 1% Nb doped PZT) thin films were prepared by a sol-gel process. They were characterized by XRD, SEM and TEM. Both crystallographic orientation and grain size of PZT films can be changed by doping. Pt/PZT/Pt capacitors were fabricated for the measurement of ferroelectric properties. By doping with both Sc and Nb, the fatigue performance of the PZT films was considerably improved and the coercive field was decreased, while the remanent polarization was not changed. In addition, the effect of dopants on the leakage current level of PZT films was studied.
Orientation and Phase Formation of Bi4Ti3O12 Film on (100) Silicon by APMOCVD and RTA
Authors: Wang H. , Su X.J. , Zeng J.M. , Wang Z. , Shang S.X. , Wang M. 
Published: April 2011

ABSTRACTBismuth titanate thin films have been grown on (100) silicon substrate by atmospheric pressure metalorganic chemical vapour deposition (APMOCVD). The phase formation of Bi-Ti-0 films are dependent upon the composition, growth temperature and RTA post-annealing process. The film grown at 550°C, under optimized growth condition, is single crystal film with (100) orientation, while the (001) preffered oriented films were obtained after rapid thermal annealing. The orientation of Bi4Ti3O12 films mainly depends upon the lattice match with the substrate. At 550°C, the best lattice match is (100) of Bi4Ti3O12 with (100) of silicon. At higher temperature (>675°C), the Bi4Ti3O12 has a tetragonal structure and the best lattice match is (001) Bi4Ti3O12 with (100) of silicon due to the different thermal expansion coefficient of two materials.
Physicochemical and Electrical Properties of RF Magnetron Sputtered Lead Zirconate Titanate Thin Films
Authors: Ea Kim B. , Hugon M.C. , Varniere F. , Agius B. , Achard H. , Puech M. 
Published: April 2011

ABSTRACTDue to their high dielectric constant, good chemical stability and good insulating properties, lead zirconate titanate (PZT) thin films are considered as promising materials to replace Si3N4 and Ta2O5 for use as the capacitor dielectric in future high density DRAMs. Moreover, the ferroelectric quality of PZT films also allows use of this material in non volatile memories. In this paper, we investigate the properties of PZT films deposited from an oxide target of nominal composition {Pb1.1(Zr0.55,Ti0.45)O3} in a radio frequency (rf) magnetron sputtering system. The Pt(deposited at 450°C)/[TiN/Ti/BPSG/Si] structure annealed at 450°C at 10−6 mbar (Pt(450°C)/{TiN/Ti/BPSG/Si}450°c,10–6mbar) was used as a substrate material in this work. The PZT films were deposited at different pressures, and different substrate temperatures ranging from floating temperature to 400°C; the thicknesses of the sputtered films were in the 15–720 nm range. The kinetics of the sputtering process and the effect of sputtering parameters on film composition have been studied and related to the continuously monitored optical emission of the plasma. The relative cation and oxygen compositions of the films were determined by a new method based on the simultaneous use of Rutherford Backscattering Spectrometry (RBS) and Nuclear Reaction Analysis (NRA) induced by a deuteron beam. The conditions for the deposition of stoichiometric PZT thin films were established.Electrical characterizations of the PZT films including resistivity, dielectric constant, dissipation factor were studied as a function of the temperature. From initial electrical measurements, it appears that a dielectric constant of 740 can be obtained for PZT 55/45 films deposited on a previously annealed Pt/TiN/Ti/BPSG/Si structure.
Microstructure Evolution of Epitaxial (Ba, Sr) TiO3/ (001) HgO Thin Films
Authors: Alyoshin V.A. , Sviridov E.V. , Hukhortov V.I.M. , Zakharchenko I.H. , Dudkevich V.P. 
Published: April 2011

ABSTRACTSurface and cross-section relief evolution of ferroelectric epitaxial (Ba,Sr)TiO3 films rf-sputtered on (001) HgO crystal cle-avage surface versus the oxygen worKing gas pressure P and subst-rate temperature T were studied. Specific features of both three-dimensional and two-dimensional epitaxy mechanisms corresponding to various deposition conditions were revealed. Difference between low and high P-T-value 3D epitaxy was established. The deposition of films with mirror-smooth surfaces and perfect interfaces is shown to be possible.
Structure and Ferroelectric Behaviour of Step-Crystallized PbZr0.5Ti0.5O3 Thin Films Prepared by Electron Beam Evaporation of Multi-Component Oxides
Authors: Darvish Shaban R. , Rastogi A.C. 
Published: April 2011

ABSTRACTPreparation of ferroelectric lead zirconate titanate (PZT) thin film by electron beam evaporation of multicomponent oxides followed by a post-deposition synthesis of PZT films by step-annealing under O2 ambient is described. Incipient formation of Pb3O4-ZrO2-PbTiO3 solid solution by a 600°C annealing is required for crystallization of PZT phase. Two morphotropic phase boundary reactions between solid solution phase with TiO2 and PbTiO3 with ZrO2 are proposed for PZT growth. Polarization and capacitance-voltage hysteresis data are presented to establish ferroelectric behaviour.
Mechanism(s) for the Suppression of the Switchable Polarization in PZT and BaTiO3
Authors: Warren William L. , Dimos Duane , Tuttle Bruce A. , Pike Gordon E. , Raymond Mark V. , Nasby Robert D. , Ramesh R. , Evans Joseph T. 
Published: April 2011

ABSTRACTSwitchable polarization can be significantly suppressed in ferroelectric (FE) materials by optical, thermal, and electrical processes. The thermal process can occur by either annealing the FE in a reducing environment or by heating it in air to 100°C while impressing a bias near the switching threshold. The optical process occurs while biasing the FE near the switching threshold and illuminating with bandgap light. And the electrical suppression effect occurs by subjecting the FE to repeated polarization reversals. Using electron paramagnetic resonance, polarization-vol tage measurements, and charge injection scenarios, we have been able to elucidate both electronic and ionic trapping effects that lead to a suppression in the amount of switchable polarization in FE materials. The relative roles of electronic and ionic effects in the same material can depend on the stress condition. For instance, in oxidized BaTiO3 crystals, optical and thermal suppressions occur by electronic domain pinning; electrical fatigue in the BaTiO3 crystals also appears to involve electronic charge trapping, however, it is suggested that these electronic traps are further stabilized by nearby ionic defects. In sol-gel PZT thin films with either Pt, RuO2, or La-Sr-Co-O electrodes it appears that the polarization suppression induced by electrical fatigue, a temperature/bias combination, or a light/bias combination are all primarily due to the trapping of electronic charge carriers to first order.
Properties of Reactively Sputter Deposited SrTiO3 Films for IR Detector Readout Electronics
Authors: Bernstein S.D. , Wong T.Y. , Rawson J.K. , Tustison R.W. 
Published: April 2011

ABSTRACTThe effects of film thickness, oxygen partial pressure, electrode type, substrate temperature, and position on the room temperature and 77 K dielectric properties of SrTiO3 (ST) films were studied. The film composition and properties vary with radial position and oxygen partial pressure. A maximum in dielectric constant occurs near the same position where stoichiometric films are obtained. The room temperature and 77K dielectric constants increase with increasing thickness, while the capacitance density decreases. Capacitance densities as high as 4 fF/μm2 were observed for films deposited at low temperature and subsequently crystallized. Elevated temperature deposition, however, results in better properties than room temperature deposition followed by annealing. Dielectric constants as high as 200 with capacitance densities up to 9 fF/μ2 were observed. For optimized deposition conditions, no dielectric break-down of the capacitors was observed at 20V after 111 days of testing. The properties of capacitors with n+Si bottom electrodes were not as good as those with Ti/Pt electrodes, however, integration with Si integrated circuit processing is expected to be much simpler.
Heteroepitaxial Growth of Ba0.5Sr0.5TiO3/SrRuO3 on YSZ/Si by Off-Axis Sputtering
Authors: Hou S.Y. , Kwo J. , Watts R.K. , Cheng J.-Y. , Cava R.J. , Peck W.F. , Fork D.K. 
Published: April 2011

ABSTRACTWe demonstrate an epitaxial heterostructure of Ba0.5Sr0.5 TiO3/SrRuO3/YSZ on Si for potential charge storage applications. The dielectric Ba0.5Sr0.5TiO3 (BST) and conductive oxide SrRuO3 are both grown (110) oriented on YSZ (100) buffered Si by 90° off-axis sputtering. These films showed a high degree of crystallinity with minimal interdiffusion at the interfaces as examined by X-ray diffraction, Rutherford backscattering spectroscopy, and cross-section transmission electron microscopy. The in-plane epitaxial alignment of the films is BST/SRO 〈111〉 // YSZ 〈110〉 with a four-fold degeneracy. The dielectric constant and loss tangent of the epi-BST films are 360 and 0.01 at 10 kHz. The leakage current density is < 4×10∼−7 A/cm2 at 1 V. The room temperature dielectric constant (ε) of the BST films shows a roll-off in the 1–10 MHz range. This is attributed to the existence of a series resistance in the measurement circuit, which likely arises from the SrRuO3 electrode.
Effects of Antiphase Domain Size and Twin Platelet Width on the Hardness of an Ordered CuAu Alloy
Authors: Shiraishi Takanobu , Ohta Michio , Nakagawa Masaharu 
Published: April 2011

AbstractEffects of antiphase domain (APD) size and inter-twin spacing on the hardness of CuAu I-phase in the overaging stage were investigated by hardness testing, transmission electron microscopy, and X-ray powder diffraction. Overaging in CuAu I-phase upon progressive ordering at 300°C was found to proceed through three stages: stages I through III. In the stage I, twinning actively occurred, and most of the coherency strains were removed. Average inter-twin spacing slightly increased. These microstructural evolutions slightly decreased the hardness of the alloy. In the stage II, both APD size and average inter-twin spacing grew larger with time, leading to a continuous decrease in hardness. In the stage III, the APD size markedly grew larger, while the growth rate of average inter-twin spacing markedly slowed down. The continuous growth of APD size apparently contributed to the further decrease in hardness. Although the crystal structure changes during the CuAu I ordering, a perfectly ordered alloy with no planar defects was suggested to be not so strong as the corresponding disordered alloy.
Ultrasonic Discrimination of Samples With Differently-Distributed Grain Sizes and Equal Average Grain Size
Authors: Nicoletti Denise , Anderson Aran 
Published: April 2011

AbstractMaterials can have distributions of grain sizes. These distributions can have effects on the material's mechanical properties that are more complicated than an average grain-size dependence. The omission of distribution effects on properties is understandable in view of the great amount of labor required in the experimental measurement of grain volume distribution, together with the predominantly two-dimensional nature of micrography-based grain-size estimation. Ultrasonic techniques have been used to nondestructively measure the grain size of materials on a scale of microns. We suggest using ultrasonic attenuation as an alternative to micrography for three reasons. One advantage is that the ultrasonic dependence on size is a true, three-dimensional dependence. Secondly, through careful selection of wavelength, various grain-size distribution parameters can be extracted. The third justification is that ultrasonic techniques are quick and nondestructive. Previous theoretical development will be reviewed, and the experimental verification will be presented. Through numerical modeling we show the advantages of using ultrasonic techniques that are sensitive to grain-size distribution parameters. We demonstrate that samples with equal average grain size but different grain-size distributions have significantly different attenuation wavelength dependencies.
Deformation Twinning and Grain Size Aspects of Numerical Simulations of Plastic Flow
Authors: Zerilli Frank J. , Armstrong Ronald W. 
Published: April 2011

AbstractThe dependence of the twinning stress on grain size is similar to the dependence of the athermal part of the flow stress on grain size. Previous numerical simulations included a twinning effect based upon the premise that twinning refines the grain size and gives additional Hall-Petch strengthening. If a grain reaches the stress level given by σT = σT0+ kT ∓-1/2, it is considered twinned and a constant increment is added to the flow stress. Once twinned, the new twinning threshold stress is much higher than the original and so further twinning is unlikely to occur. The twinning model used in this work is based on the idea that enough twinning will occur in a grain to accommodate the excess by which the Von Mises equivalent stress exceeds the twinning threshold stress. The previous twinning model required knowledge of the number of twins per grain produced. With this model, the parameters for iron are known a priori (σT0 = 330 MPa and kT = 2.8 MPa m1/2) and numerical simulations of Taylor cylinder impacts produced good agreement with experimental results. For titanium and zirconium, σT0 and kT were determined by matching the computed and experimental shapes. The results here indicate that twinning hardens these metals by effectively changing the material grain size and the microstructure within the grains.
Applications of Images Digital Analysis in the Characterisation of Grains Morphology Influence in Mechanical Behaviour of Granular Soils
Authors: G Bonifazi , G Sappa , G De Casa 
Published: April 2011

AbstractPreliminary results of a research aimed to identify the influence of the morphological characteristics of the grains constituting a quartz sand on the mechanical behaviour of the sand itself are presented. The tests were conducted on different size class samples resulting from a grain-size classification of the sand following the international standard classification (ASCII) procedure. For each sample traditional direct shear laboratory tests and an accurate characterisation of morphological and morphometrical properties of their constituting elements (grains) by means of digital image processing techniques were conducted. The statistical distribution of the different parameters derived following the two above mentioned procedures was studied and the results discussed.
Formation and Spatial Statistics of Spherulitic Grain Pattern in Solidified Films of Isotactic Polypropylene
Authors: Huang Tao , Rey Alejandro D. , Kamal Musa R. 
Published: April 2011

AbstractImage analysis and measurements on forimation and spatial statistics of spherulitic grain pattern in solidified films of a model polymer, isotactic polypropylene (iPP), have been carried out during in-situ observation experiments under isothermnl conditions. Topological correlations and geometrical distribution fuinctions of polymer grain sides and area are reported. Some topologically unstable configurations, such as multi-vertices, “T” type vertices and two sided grain (lens), have been found. Analysis by spatial tessellations shows that the tenWal evolution and spatial distributions of nuclei point patterns play a role in all of these microstructural properties.