bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical Losses in Ferroelectric Oxide Thin Films: Is There Light at the End of the Tunnel?
Authors: Fork D. K. , Armani-Leplingard F. , Kingston J. J. 
Published: April 2011

ABSTRACTOptical losses are a barrier to use of ferroelectric waveguide thin films. Losses of about 2 dB/cm will reduce the efficiency of a frequency doubler by over 50%. Achieving losses on this order in conjunction with other essential film properties is difficult. The optical loss has several origins, including absorption, mode leakage, internal scattering and surface scattering. When the film surface morphology is accurately known, it is possible to estimate the surface scattering component of the loss. We have employed atomic force microscopy and computer modeling to compute, and correlate the optical loss as a function of film thickness and wavelength. The results suggest upper limits to the morphological roughness for various device applications. For lithium niobate films on sapphire which are intended to frequency double into the blue part of the spectrum, the optimal film thickness is about 400 nm and the RMS roughness is constrained below about 1.0 nm, with some weak dependence on grain size. Although present growth techniques do not appear to achieve this level of surface flatness intrinsically, an understanding of the morphological development of the film structure may lead to improvements.
Pulsed Laser Deposition of Epitaxial Sr0.61Ba0.39Nb2O6 Thin Films for Waveguide Applications
Authors: Youden K.E. , Schwyn Thöny S. , Hesselink L. , Harris J.S. 
Published: April 2011

ABSTRACTWe report the epitaxial growth of Sr0.6iBa0.39Nb2O6 (SBN) thin films on MgO substrates by pulsed laser deposition. Rutherford backscattering analysis shows that the films have stoichiometric composition, identical to the target, and thicknesses in the range 200–400 nm. X-ray diffraction 2θ-scans indicate layers with the (001) orientation perpendicular to the substrate plane, and phi scans on the (221) plane reveal that the films have two pairs of in-plane orientations. The orientations correspond to a rotation of the SBN unit cell relative to the MgO unit cell of ± 18.6° and ± 30.9° respectively. Waveguide characterization shows waveguides supporting up to four modes and film refractive indices which compare well with those of bulk SBN.
Influence of the Ferroelectric Phase Transition on the Photoelectrical Properties of the P-N Junctions
Authors: Lupu Anatol T. , Grishechkina Svetlana P. 
Published: April 2011

ABSTRACTPhotoelectrical properties of the p-n junctions on the base of Pb1−xGexTe were investigated. A number of anomalous phenomena below Tc such as: the change of the photovoltage sign, low frequency maximum in the temperature dependence of the junction capacitance and feature near the edge of the spectral dependence were observed.To explain the obtained results a model considering screening of spontaneous polarization outside the junction was proposed. This work gave for the first time experimental evidence concerning the model of polarization switching in ferroelectric with p-n junction.
Electrode Contacts on PZT Thin Films and Their Influence on Fatigue Properties
Authors: Lee J.J. , Thio C.L. , Bhattacharya M. , Desu S.B. 
Published: April 2011

ABSTRACTThe degradation (fatigue) of dielectric properties of ferroelectric PZT (Lead Zirconate Titanate) thin films during cycling was investigated. PZT thin films were fabricated by metal-organic decomposition (MOD). Samples with electrodes of platinum (Pt) and ruthenium oxide (RuO2) were studied. The interfacial capacitance (if any) at the Pt/PZT and RuO2/PZT interfaces was determined from the thickness dependence of low-field dielectric permittivity (εr) measurements. It was observed that a low εrlayer existed at the Pt/PZT interface but not at the RuO2/PZT interface. The dielectric permittivity of this interfacial layer degrades with increasing fatigue while the εrof the bulk PZT film remains constant. This indicates that fatigue increases the interfacial layer thickness but does not change the bulk properties. For the capacitors with RuO2/PZT/RuO2 structure, however, the εdoes not change with thickness and fatigue cycling. This implies no interfacial layer exists between RuO2/PZT and, therefore, no fatigue was observed. Additionally, an impedance spectroscopie technique has been proposed for possible use in analyzing the nature of the interfacial layer during the fatigue process.
Effects of A.C. Stress on Charge and Voltage Decay Rates of PZT Thin Film Capacitors for DRAM Applications
Authors: Khamankar Rajesh B. , Kim Jiyoung , Jiang Bo , Lee Jack 
Published: April 2011

ABSTRACTA PZT thin film capacitor displays a reduction in the charge storage density (Qc') after the device has undergone pulsed electrical stress. This changes the charge-voltage relationship for the devices. The effect of this change in the Q-V relationship on the DRAM READ time is described. Measurements of the charge and voltage decay rates have been previously identified as ideal techniques for characterizing signal loss. For the first time the effects of electrical stress on these rates have been studied. While the charge decay rate decreases with an increase in the number of stress cycles for both the bipolar and unipolar stress, the voltage decay rate decreases after unipolar stress but it increases for bipolar stress at lower stress voltages. The implications of these results on the DRAM performance shall be discussed.
Microstructural and Electrical Characterization of Barium Strontium Titanate Thin Films
Authors: Wu Yujing , Jacobs Elizabeth G. , Pinizzotto Russell F. , Tsu Robert , Liu Hung-Yu , Summerfelt Scott R. , Gnade Bruce E. 
Published: April 2011

ABSTRACTThe kinetics of BST thin film grain nucleation and growth caused by rapid thermal annealing have been investigated. A series of Ba0.67Sr0.33Tii0.5O3 films were deposited on Pt electrodes using a metal-organic decomposition process. The effects of anneal time and temperature on BST grain sizes were studied by altering the processing conditions during RTA. A series of films were annealed by RTA at temperatures ranging from 550°C to 950°C for times ranging from 30 to 120 seconds. Crystallographic and microstructural characterization were done using XRD and TEM. The XRD results indicated that BST grain size increased with increasing anneal temperature, but was not affected by anneal time. Plan-view TEM indicated that BST grains were imbedded in an amorphous matrix. The average grain size was on the order of 200 Å.
Pulsed Laser Deposition of Bi4Ti3O12 Thin Films on Sapphire Substrates
Authors: Jo William , Noh T.W. 
Published: April 2011

ABSTRACTUsing pulsed laser deposition, Bi4Ti3O12 thin films were grown on (0001) and (1102) surfaces of Al2O3. Substrate temperature from 700 to 800 °C and oxygen pressure from 50 to 1000 mtorr were varied, and their effects on Bi4Ti3O12 film growth behavior was investigated. Only for a narrow range of deposition parameters, can highly oriented Bi4Ti3O12(104) films be grown on Al2O3(0001). Further, epitaxial BTO(004) films can be grown on Al2O3(1102). The growth behavior of preferential BTO film orientations can be explained in terms of atomic arrangements in the Bi4Ti3O12 and the Al2O3 planes.
Correlations of Ba1−xSrxTiO3 Materials and Dielectric Properties
Authors: Tsu Robert , Liu Hung-Yu , Hsu Wei-Yung , Summerfelt Scott , Aoki Katsuhiro , Gnade Bruce 
Published: April 2011

ABSTRACTThin film barium strontium titanate, Ba1−xSrxTiO3 (BST), has been deposited on Pt bottom electrodes using metal-organic decomposition (MOD). Optimization of BST electric properties, including capacitance density and leakage current, can be achieved by altering the chemical and microstructural attribute of the films. Dielectric properties of BST are strongly dependent on processing temperature, film thickness, composition, and microstructure, which are closely correlated with each other. Nucleation temperatures of BST range from 580°C – 650°C depending on film thicknesses. The chemical composition giving the highest dielectric constant is explained in terms of microstructure; capacitance increases with increasing grain size for the BST films in this study. Capacitance density of 50 fF/μ m2 and leakage current density < 100 nA/cm2 at 1.6 V can be achieved by optimizing BST materials properties. In addition, leakage conduction through the Pt/BST/Pt capacitor is shown to consist of polarization current resulting from Debye relaxation and true leakage current attributed to Schottky electron emission.
SrTiO3 Films Prepared by MOCVD Using Novel Sr Source
Authors: Yamauchi Hideaki , Kimura Takafumi , Yamada Masao 
Published: April 2011

ABSTRACTSrTiO3 thin films have been prepared by MOCVD. A novel Sr source of Sr(DPM)2-tetraen2 was used to stabilize source delivery and to reduce the vaporization temperature of Sr source. Films were deposited on Pt/Ta/Si substrates at deposition temperatures from 450 °C to 600 °C. The relative dielectric constant was about 220 at the deposition temperatures from 550 °C to 600 °C for as-deposited 90-nm-thick films. The leakage current density was in the range of 10−7 A/cm2, typically.
Improved Electrical Properties of SrTiO3, Thin Films by Electron Cyclotron Resonance Plasma Chemical Vapor Deposition
Authors: Yabuta Hisato , Takemura Koichi , Yamaguchi Hiromu , Sone Shuji , Sakuma Toshiyuki , Yoshida Masaji 
Published: April 2011

ABSTRACTSrTiO3 thin films with various compositions have been prepared on Pt coated sapphire substrates by electron cyclotron resonance plasma chemical vapor deposition at 450 °C and 600 °C. The stoichiometric (Sr/(Sr+Ti)=0.50) films have maximum dielectric constants (εr) of 190 for the 600 °C deposition and 170 for the 450 °C deposition. The dielectric constant decreases abruptly with increasing or decreasing the Sr/(Sr+Ti) value from the stoichiometry, especially for the 450 °C deposition. The Ti-rich films include titanium suboxide (TiOx). In the Sr-rich films, excess SrO is thought to be inserted into the SrO plane and TiO2 plane in SrTiO3. In addition, SrCO3 is included in Sr-rich films. The concentration of these impurities is greater for the 450 °C deposition than for the 600 °C deposition. The leakage current density increases with increasing the Sr/(Sr+Ti) value, and the leakage current density for the 450 °C deposition is larger than for the 600 °C deposition in the Sr-rich composition region. These impurity phases may be related to the higher leakage current density. These results suggest that precise composition control in stoichiometry is necessary to deposit SrTiO3 films with superior electrical properties.
Structural and Leakage Current Behavior of Bi4Ti3O12 Thin Films on La0–5Sr0–5jCoO3 Bottom Electrodes Grown by Pulsed Laser Deposition
Authors: Jo William , Kim K.H. , Noh T.W. , Kwon S.D. , Choe B.D. , You B.D. 
Published: April 2011

ABSTRACTUsing La0.5Sro.5CoO3 bottom electrode layers, Bi4Ti3O12 thin films were grown on LaAlO3(001), Al2O3(0001), and Si(001) substrates. Crystalline orientation of the Bi4Ti3O12 thin films was examined by x-ray diffraction techniques. The cross-sectional microstructures of Bi4Ti3O12/La0.5Sr0.5CoO3 heterostructures are investigated. It is found that the crystalline orientation and the microstructure affect leakage current behavior of the Bi4Ti3O12 layers.
Growth and Characterization of PbTiO3 and Pb(Zr,Ti)O3 Thin Films by MOCVD
Authors: Gao Y. , Dong W. , Turtle B.A. 
Published: April 2011

ABSTRACTFerroelectric PbTiO3 and Pb(Zr,Ti)O3 thin films with a perovskite structure were grown on MgO and Pt/Ti/SiO2/Si by MOCV.D. The microstructure and composition of the films were characterized by x-ray diffraction, SEM, and AES. Preferred orientation of either (111) or (100)/(001) was obtained on the Pt/Ti/SiO2/Si substrates at temperatures from 600 °C to 650 °C The preferred (111) orientation was attributed to the formation of the Pt3Ti phase in the Pt layer of the substrates, whereas the (100)/(001) orientations were inferred as the growth rate effect. AES depth profiling indicated a uniform composition through the thickness of the PZT films. However, SEM showed different topography and microstructure of the PZT films deposited in different oxygen partial pressure. Electrical properties of the PZT films appear varied as a function of the oxygen partial pressure in the reactor.
Effects of Acetylacetone Additions on PZT Thin Film Processing
Authors: Schwartz Robert W. , Assink R.A. , Dimos D. , Sinclair M.B. , Boyle T.J. , Buchheit C.D. 
Published: April 2011

ABSTRACTSol-gel processing methods are frequently used for the fabrication of lead zirconate titanate (PZT) thin films for many electronic applications. Our standard approach for film fabrication utilizes lead acetate and acetic acid modified metal alkoxides of zirconium and titanium in the preparation of our precursor solutions. This report highlights some of our recent results on the effects of the addition of a second chelating ligand, acetylacetone, to this process. We discuss the changes in film drying behavior, densification and ceramic microstructure which accompany acetylacetone additions to the precursor solution and relate the observed variations in processing behavior to differences in chemical precursor structure induced by the acetylacetone ligand. Improvements in thin film microstructure, ferroelectric and optical properties are observed when acetylacetone is added to the precursor solution.
Rapid Thermal Processing and Crystallization Kinetics in Lead Zirconate Titanate (PZT) Thin Films
Authors: Griswold E.M. , Weaver L. , Calder I.D. , Sayer M. 
Published: April 2011

ABSTRACTRapid thermal processing (RTP) has been used to examine the crystallization kinetics of lead zirconate titanate (PZT) fabricated using a sol gel process. Depth profiling of PZT films was performed with glancing angle x-ray diffraction and transmission electron microscopy. The films were annealed using RTP ramp rates from 10°C/s to 200°C/s and hold temperatures from 525°C to 650°C. The effect of ramp rate on the phase transformation is presented, and the growth of oriented columnar structures is demonstrated. Films subjected to RTP at 650°C for 1s using a ramp of 10°C/s began to transform to perovskite and were ferroelectric while a ramp of 100°C/s (same hold) produced a linear material which was pyrochlore. Longer hold conditions such as 650°C for 30s produced ferroelectric films with Pr in excess of 20μC/cm2 and relative permittivities ε > 600.
The Pyrochlore-to-Perovskite Transformation in Solution-Derived Lead Zirconate Titanate Thin Films
Authors: Voigt James A. , Tuttle B.A. , Headley T.J. , Lamppa D.L. 
Published: April 2011

ABSTRACTWe have characterized the pyrochlore-to-perovskite crystallization process in solution-derived Pb(Zr0.20Ti0.80)O3 thin films on (100) MgO single crystal substrates. It has been determined that the perovskite phase nucleated preferentially at the film/MgO interface out of a nanocrystalline (≈100Å grains) pyrochlore matrix. During the early stages of the pyrochlore-to-perovskite conversion process, perovskite growth proceeded nearly isotropically from the substrate to form hemispherically shaped grains. Deviations from isotropie growth were shown to result from a growth dependence based on the crystallographic orientation of a growing perovskite grain relative to the orientations of pyrochlore grains being transformed. The volume change that occurs during the pyrochlore-to-pervoskite transformation along with two-dimensional grain growth has been used to develop a mechanism for formation of porosity that commonly is concentrated in grain boundary regions.
Effect of Microstructure on the Electrical Characteristics of Sol-Gel Derived PZT Thin Films
Authors: Kim Jiyoung , Khamankar Rajesh , Jiang Bo , Mamar Papu , Moazzami Reza , Jones Robert E. , Lee Jack C. 
Published: April 2011

ABSTRACTThe effects of the microstructure of PZT sol-gel thin films, processed using different solutions, on their material and electrical properties have been studied. The films have different degrees of preferred orientation of the perovskite crystals as well as different grain size. The material characteristics are evaluated using SEM micrographs and XRD. Correlation of these material properties with the electrical properties for both NVRAM and DRAM applications is made.
Construction of Strained SrTiO3/BaTiO3 Superlattices and Their Dielectric Properties
Authors: Tabata Hitoshi , Tanaka Hidekazu , Kawai Tomoji 
Published: April 2011

ABSTRACTArtificial dielectric superlattices of SrTiO3/BaTiO3(STO/BTO) and CaTiO3/BaTiO3 (CTO/BTO) have been formed by a pulsed laser ablation technique with an in situ monitoring of RHEED (reflection high energy electron diffraction) oscillation. The crystal structures can be controlled with atomic order accuracy and a large stress of 400–500 MPa is introduced at the interface between the BTO and STO layers. Xhe superlattices show higher dielectric constant than that of (Sr0.5Ba0.5)TiO3 films against the change of temperature or applied frequency. A large dielectric constant of 900 was observed for the superlattices with a stacking periodicity of 2 unit cells / 2 unit cells. Xhe superlattices show drastically different electrical behavior from that of the solid solution (Sr,Ba)XiO3 films, both with changing temperature and applied frequency. Broad maxima of the dielectric constants occur around 40–50 °C and the values remain large even for the temperature above 200 °C. On the contrary, in the case of CTO/BTO superlattices, lattice constants and dielectric constant do not change so much compared with STO/BTO cases. Lattice mismatch in the STO/BTO and the CTO/BTO superlattices are 2.5% and 5.5%, respectively. In the case of CTO/BTO, misfit dislocations such as stacking faults may occur at the interface between CTO and BTO layers owing to large lattice mismatch. Therefore, lattice strain is introduced effectively below the lattice mismatch of about 3%.
Thickness Dependence of Induced Ferroelectricity in Epitaxially Grown Ba0.44Sr0.56TiO3 Thin Films
Authors: Abe Kazuhide , Komatsu Shuichi 
Published: April 2011

ABSTRACTBa0.44Sr0.56TiO3 (BST) thin films with various thicknesses were epitaxially grown on Pt/MgO(100) substrates with rf magnetron sputtering. The thickness dependence of lattice constant, D-E hysteresis and dielectric constant were evaluated for the BST films. The lattice constant in the thickness direction is elongated through the thickness range (33 to 221 nm), whereas the ferroelectric and the dielectric properties had strong thickness dependencies. The mechanism of the induced ferroelectricity is discussed in terms of the thickness dependence and deposition technique.
Effects of Excess Pb on Crystallization and Electrical Properties of Ferroelectric PZT Films Deposited by Reactive RF Magnetron Sputtering
Authors: Bernstein S.D. , Wong T.Y. , Collins S.R. , Kisler Yanina , Tustison R.W. 
Published: April 2011

ABSTRACTFilms were deposited onto unheated, Ti/Pt coated Si substrates by reactive sputtering in an argon-oxygen atmosphere from a sintered PZT target, and subsequently crystallized at temperatures between 550 and 650 °C. Pt/PZT/Pt capacitors were formed by ion beam sputtering of top electrodes through a shadow mask. Electrical properties were found to depend on gas pressure during deposition. This effect is interpreted in terms of variations in film stoichiometry (particularly Pb content). Films with large excesses of Pb were found to exhibit high leakage currents and poor ferroelectric behavior, whereas films with lower excesses of Pb had low leakage currents, and good ferroelectric properties. Films with the largest Pb excess had a random orientation, while the film with the lowest Pb excess had a preferred (111) orientation. With 550 °C crystallization temperatures the films consist of a mixture of ferroelectric perovskite phase and either PZT pyrochlore or PbO. At higher crystallization temperatures no pyrochlore is detected.
Liquid Phase Epitaxy of Na1−yKyTa1−xNbxO3 for Pyroelectric Applications
Authors: Sitar Z. , Gutmann R. , Pierhöfer H. , Günter P. 
Published: April 2011

ABSTRACTThe epitaxial growth of para- and ferroelectric KTa1−xNbxO3 (KTN) thin films was achieved in an in-house built liquid phase epitaxy (LPE) apparatus. Films were grown from a KF/NaF/KTN solution on KTaO3 substrates. Growth rates of several μ/min were achieved at a growth temperature of 1200 K. Up to 150 μm thick, smooth KTN films with different compositions were grown and characterized. Almost perfect lattice matching was achieved by the addition of NaF to the KF flux. Partial replacement of K by Na did not result in a significant change of physical properties of KTN.The investigation of the dielectric properties revealed a sharp change of the dielectric constant at the ferroelectric phase transition. The ferroelectric domain structure was modified by poling at 1kV/cm. Pyroelectric studies yielded a pyroelectric coefficient of up to 5.2 mC/m2K while the frequency dependence of the pyroelectric response showed a maximum at 230 Hz.
Imprint of La-Sr-Co-O/Pb-La-Zr-Ti-O/La-Sr-Co-O Heterostructures Grown by Pulsed Laser Deposition
Authors: Lee J. , Ramesh R. , Keramidas V.G. 
Published: April 2011

ABSTRACTLa-Sr-Co-O(LSCO)/Pb-La-Zr-Ti-O(PLZT)/La-Sr-Co-O heterostructures with different crystalline quality have been grown on LaAlO3 and Si with a bismuth titanate template layer. Imprint of the heterostructures are investigated in comparison with fatigue and retention. Oxygen ambient during cooling the heterostructures was also varied to investigate the imprint. With consideration of the switching behavior caused by imprint, imprint behavior was deconvoluted from fatigue and retention. In epitaxial PLZT capacitors grown on LaAlO3, imprint behavior was found to be significantly dependent on the oxygen ambient. As the oxygen ambient became more reducing, the capacitors developed more voltage asymmetry in hysteresis loops and a more preferred polarization state directed towards the top electrode. On the other hand, oriented PLZT capacitors exhibited less pronounced effect of the oxygen ambient on the imprint behavior.
Can We Exploit Imprint in Ferroelectric Thin Film Capacitors for Memory Applications?
Authors: Yoo In Kyeong , Desu Seshu B. 
Published: April 2011

ABSTRACTImprint was observed for fatigued PZT (Zr/Ti = 53/47) capacitors which were subjected to a thermal cycle (at 80°C for a period of time). It was also observed for capacitors whose top electrode was defined by ion milling. In addition, capacitors with an asymmetric multilayered structure showed severe imprint problems. Based on the above observations, imprinting was categorized as:1) Intrinsic imprint which is caused by inherent conditions such as device structure, configuration, and material composition.2) Extrinsic imprint which is generated by external sources such as electrical stress, thermal stress, time, and processing.Imprint mechanisms were discussed for each imprinting category. Most importantly, based on partial switching, a new memory logic was suggested. It is shown that stable imprinting may be useful for low density FRAM applications when the proposed new memory logic is applied. Reliability of the new logic was also shown to be significantly better than conventional operation.