bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microwave Dielectric Properties of LaScO3-TiO2 Materials
Authors: Kwon Do-Kyun , Lanagan Michael T. , Shrout Thomas R. 
Published: April 2011

ABSTRACTFrom fundamental ionic polarizability concepts, LaScO3 was projected as a candidate dielectric material for microwave application. The microwave dielectric properties of LaScO3 were obtained as the dielectric permittivity of 24, Q×f of 18,000 GHz, with a temperature coefficient of resonant frequency (TCF) of −69 ppm/°C. Solid solutions and polyphase assemblages were investigated in the LaScO3-TiO2 system as a function of TiO2 content, and correlated with the microwave dielectric properties. Orthorhombic perovskite LaScO3 transformed to tetragonal symmetry with Ti substitution on the B-site of LaScO3 owing to the ionic radius difference between Sc3+ and Ti4+. With this phase transition, the formation of A-site vacancies (VLa‴) resulted in the precipitation of a La deficient secondary phase. The substitution of Ti also affected the dielectric properties. The dielectric constant increased and TCF became less negative with increased TiO2 addition. However, the Q×f value decreased, due to the formation of the secondary phase. For the case of the 0.6LaScO3-0.4TiO2 composition, a dielectric K of 40, Q×f of 6,000 GHz and nearly zero TCF were obtained.
High-Density, Low-loss MOS Decoupling Capacitors integrated in a GSM Power Amplifier
Authors: Roozeboom F. , Kemmeren A. , Verhoeven J. , van den Heuvel E. , Kretschman H. , Frič T. 
Published: April 2011

ABSTRACTHigh-density MOS capacitors have been fabricated with ∼ 30 nF/mm2 specific capacitance on highly-doped Si-wafers with arrays of macropores with ∼ 2 μm diameter. Using the Bosch process [1] these pores were dry-etched to depths of ∼ 30 μm or more. The enlarged Si-surface thus obtained serves as a substrate for capacitors fabricated by fully MOS-compatible processing.Wafers were fabricated with a top electrode of poly-Si and Al and ‘ONO’ (i.e. oxide / nitride / oxide) dielectric stacks showing 7–10 MV/cm electrical breakdown field and leakage < 1 nA/mm2 @ 20 V. These wafers were thinned to 380 μm and sawn into dies, representing 40 nF capacitors. Typically low loss factors such as ESR < 50 mΩ and ESL < 20 pH and resonance frequencies of ∼ 0.1 GHz were found for 40 nF capacitor dies. Next, 40 nF dies were mounted by wire bonding on Al2O3 or laminate substrate as supply-line decoupling capacitors in complete GSM power amplifier test modules. RF decoupling and transmission were measured and compared to identical test modules with conventional discrete ceramic capacitors. The MOS capacitors showed very efficient decoupling, resulting in superior signal stability as measured in the 0 – 1 GHz range (less noisy, free from oscillations).The new capacitor is very suitable for integrated decoupling purposes, e.g. supply-line decoupling in RF wireless communication and analog and mixed-signal systems.
RF-MEMS: Materials and technology, integration and packaging
Authors: Tilmans Harrie A. C. 
Published: April 2011

ABSTRACTMEMS technology is rapidly emerging as an enabling technology to yield a new generation of highperformance RF-MEMS passives, like switches, tunable capacitors, high-Q resonators and tunable filters. This paper presents the progress in RF-MEMS device and package development with focus on relevant technology and material issues. The importance of wafer-level or 0-level packaging of the RF-MEMS devices is elucidated. Examples of 1-level packaging, e.g., chip-on-board or plastic molded 1-level package, are briefly described. The paper concludes in stipulating how integration of RF-MEMS passives with other passives (as inductors, LC filters, SAW devices) and active circuitry (RFICs) can lead to so-called “RF-MEMS system-in-a-package (RF-MEMS-SiP)” modules. The evolution of the RF-MEMS-SiP technology is illustrated using IMEC's microwave multi-layer thin film MCM-D technology.
Photodefinable Metal Oxide Dielectrics: A Novel Method for Fabricating Low Cost RF Capacitive MEMS Switches
Authors: Wang Guoan , Jeyakumar Augustin , Papapolymerou John , Henderson Clifford L. 
Published: April 2011

ABSTRACTIn this paper, a novel approach for fabricating low cost capacitive RF MEMS switches using directly photodefinable high dielectric constant metal oxides has been developed. In this approach, a radiation sensitive metal-organic precursor is deposited via spin coating and converted patternwise to a high dielectric constant metal oxide via ultraviolet exposure. The feasibility of this approach is demonstrated by fabricating bridge-type and cantilever-type switches with a nitride/metal-oxide/nitride dielectric film stack. These switches exhibited significantly higher isolation and load capacitances as compared to comparable switches fabricated using a simple silicon nitride dielectric.
Pyroelectric Properties of Ferroelectric Thin Films: Effect of Internal Stresses
Authors: Sharma A. , Ban Z.–G. , Alpay S. P. 
Published: April 2011

ABSTRACTA thermodynamic model is employed to analyze the effect of internal stresses on the pyroelectric response of ferroelectric thin films. The pyroelectric coefficient as a function of the misfit strain is calculated for (001) Ba0.6Sr0.4TiO3 epitaxial thin films by taking into account formation of misfit dislocations that relieve epitaxial stresses during deposition. It is shown that the pyroelectric response is highly dependent on the misfit strain in epitaxial thin films. Enhanced pyroelectric coefficient can be achieved by adjusting the misfit strain via substrate selection and film thickness especially in the vicinity of the ferroelectric to paraelectric phase transformation.
Deposition Of BaTiO3 Thin Films And MgO Buffer Layers On Patterned GaAs Substrates For Integrated Optics Applications
Authors: Chen Ding-Yuan , Murphy Timothy E. , Phillips Jamie D. 
Published: April 2011

ABSTRACTThis work addresses the need for thick layers of ferroelectric thin films on semiconductors for integrated optics applications. The deposition of BaTiO3 thin films with MgO buffers on patterned GaAs substrates is presented as an approach to achieve crack-free optical waveguiding structures. Cracking and peeling of the thin films are observed on patterns with lateral dimensions exceeding 60 microns and nearly crack-free thin films for patterns with lateral dimensions of a few microns. The cracking and peeling of the thin films is attributed to thermal expansion mismatch during the heating and cooling steps of the deposition process. A thin film stress and fracture model is used to analyze the phenomenon. Reduced cracking and peeling on the patterned features are attributed to strain relief on the patterned features. The inclusion of thick AlxOy buffer layers obtained through wet-oxidation of AlGaAs prior to BaTiO3/MgO deposition are presented as a means of obtaining electro-optic waveguide structures on GaAs.
An Effective Way to Suppress the Pyrochlore Phase Formation in SBT Thin Films
Authors: Jung Se-Yeon , Kwak Woo-Chul , Hwang Seung-Joon , Sung Yun-Mo 
Published: April 2011

ABSTRACTSr0.7Bi2.4Ta2O9 (SBT) thin films were deposited on Pt/Ti/SiO2/Si substrates with and without a seed layer of ∼40 nm thickness using sol-gel and spin coating methods. The influence of seed layer on the phase formation characteristics of SBT thin films was investigated using x-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Formation of pyrochlore as well as Aurivillius phase was observed in both the unseeded and seeded SBT films heated at 740°C. However, it was revealed that Aurivillius phase formation was enhanced in seeded SBT thin films and pyrochlore phase formation was highly suppressed. In this study, two possible mechanisms for the suppression of pyrochlore phase formation were proposed from the perspectives of activation energy difference for Aurivillius and pyrochlore phase formation and Bi-ion diffusion to pyrochlore phase.
Polarization Enhancement of Nd-Modified Bismuth Titanate Prepared by Pulsed Laser Deposition at Low Temperature
Authors: Wenbiao Wu , Akira Shibuya , Minoru Noda , Masanori Okuyama 
Published: April 2011

ABSTRACTNeodymium-modified Bi4Ti3O12(BNdT) thin films have been prepared by pulsed laser deposition (PLD), aiming to realize enhanced ferroelectric properties by a low temperature treatment. When deposited at 500°C, the film shows P-E hysteresis having twice remanent polarization 2Pr of 78.8 μC/cm-2, coercive force Ec of about 250 kV/cm, and leakage current of less than 10-7 A/cm2 from -50 to +50 kV/cm. Good fatigue properties of BNdT films deposited at 5 Hz have been obtained up to 1010 cycles of 500 kHz bipolar square pulses, with less than 25% decrease of +Pr and -Pr.
Preparation and Characterization of Ba1-xSrxTiO3 Based Thin Films for Pyroelectric Applications
Authors: Hubbard C. W. , Cole M. W. , Ervin M. , Wood M. 
Published: April 2011

ABSTRACTThe use of pyroelectric thin films in uncooled IR detectors has many advantages over the present IR detector technology, which requires extensive cooling for operation. These advantages include reduced weight, reduced footprint, reduced complexity, increased reliability, and decreased maintenance. Ba1-xSrxTiO3 (BST), based thin films are ideal candidates for use in these devices due to their tailorable materials properties. These properties include a high dielectric constant, low dielectric loss, high electrical resistivity, as well as a high pyroelectric constant. BST thin films were doped with Mg in varying amounts, from 0 to 20mol%. The thin films were deposited via metalorganic solution deposition (MOSD) on Pt/Ti/SiO2/Si substrates. Annealing temperatures ranged from 500 to 750 °C. The films were characterized for structural, microstructural, compositional, surface morphological, dielectric and insulating properties. Glancing angle x-ray diffraction (GAXRD) was used to determine crystallinity, phase formation and film orientation. Field emission scanning electron microscopy (FESEM) and cross sectional transmission electron microscopy (TEM) were employed to access surface morphology and microstructure. The Materials Detectivity Figure of Merit (FOM), D*, [D*=pi/(CV(ε0εrtanδ)1/2] was used to evaluate the film's detectivity response. Our results show that undoped Ba60Sr40TiO3, with a value D*= 0.08 (cm3/J)1/2, appears to out perform Pb based pyroelectric thin films, thus making it a viable candidate for IR pyroelectric detector applications.
Ferroelectric Domain Structure and Local Piezoelectric Properties of Sol-Gel Derived Pb(Zr1-xTix)O3 Films
Authors: Bdikin I. K. , Shvartsman V. V. , Kholkin A. L. , Kim Seung-Hyun 
Published: April 2011

ABSTRACTHigh-resolution domain studies are performed on Pb(Zr1-xTix)O3 (PZT) films of different thicknesses and compositions (x=0.30, 0.48, and 0.70) by piezoresponse force microscopy (PFM). Depending on the composition, the orientation of the films is varied from purely (111) (related to the orientation of Pt bottom electrode) to a more random texture. Statistical processing of the obtained domain images is used to analyze the correlation between the composition of the films and their nanoscale piezoelectric properties. It is shown that the virgin (unpoled) films possess large piezoelectric activity comparable to that after local poling (self-polarization effect). This corresponds to a clear predominance of the domains with polarization oriented from the free surface of the film to the bottom electrode. Both the average piezoelectric signal and half-width of the piezoelectric histograms depend on the composition and thickness of the films. The largest local piezoelectric coefficient and the broadest distribution are found for tetragonal (x=0.70) films with almost pure (111) texture. The results are discussed in terms of texture and PFM instrumentation effects on local piezoelectric measurements.
Compositionally Asymmetric Tri-Color Superlattices Grown by Pulsed Laser Deposition
Authors: Lee H. N. , Christen H. M. , Rouleau C. M. , Senz S. , Lee S. K. , Hesse D. , Lowndes D. H. 
Published: April 2011

ABSTRACTCompositionally asymmetric tri-color superlattices (TCS) with a combination of BaTiO3/SrTiO3/CaTiO3 have been grown by pulsed laser deposition (PLD) on atomically-flat SrRuO3-covered (001) SrTiO3 substrates. Conducting SrRuO3 films with single-terrace steps that closely mimic those of the SrTiO3 substrate also were grown by PLD and serve as bottom electrodes. In order to achieve atomic control of each layer, we have calibrated precisely the number of laser pulses required to grow one unit-cell-thick layers (∼200 for a laser spot of 0.4 mm2). These conditions allowed recording of pronounced oscillations of the reflection high-energy electron diffraction (RHEED) specular spot intensity over the entire growth run - even for TCS layers totaling more than 1000 nm in total thickness.
Low Temperature Crystallization of Bismuth Layer-Structured Ferroelectric Thin Films Using Lead Titanate Sol-Gel Templating Technique and Their Electrical Properties
Authors: Karasawa Junichi , Kijima Takeshi , Natori Eiji , Shimoda Tatsuya 
Published: April 2011

ABSTRACTThe crystal structure and electrical properties of lead titanate (PbTiO3: PT) sol-gel network templated bismuth layer-structured ferroelectric (BLSF) thin films were systematically investigated as a function of the doping amount of lead titanate sol-gel solution and annealing temperature. The starting solutions of lead titanate sol-gel templated BLSF were prepared by adding lead titanate sol-gel solution to BLSF solutions such as strontium bismuth tantalate (SrBi2Ta2O9: SBT), bismuth titanate (Bi4Ti3O12: BiT) and lanthanum-doped bismuth titanate ((Bi,La)4Ti3O12: BLT). These solutions were spin-coated on platinized silicon wafers and pyrolized on a hot plate, then crystallized at 550°C – 738°C by RTA (Rapid Thermal Annealing). The crystallized films with sputtered platinum top electrodes were post-annealed for electrical property measurements. In the case of SBT-PT, it was found that the added lead titanate so-gel network has no remarkable effect on lowering the BLSF (m=2) crystallization temperature but rather enhances the pyrochlore phase. In the case of BiT-PT, the bismuth layered-structure was confirmed at the temperature down to 550°C as the amount of lead titanate sol-gel network is increased. The major layered-structure, however, was not desired m=3, but unexpected m (e.g m=4 or higher). In the case of BLT-PT, lowering the BLSF (m=3) crystallization temperature down to 638°C was finally achieved within proper amount of lead titanate sol-gel network without drastic drop of ferroelectricity. A 2Pr of 32 μC/cm2 was obtained in 0.96BLT-0.04PT thin film.
Time-domain Terahertz Spectroscopy of Strontium Bismuth Tantalate Thin Films
Authors: Kotani K. , Misra M. , Kawayama I. , Tonouchi M. 
Published: April 2011

ABSTRACTWe have measured the dielectric and optical properties of pulsed laser deposited SrBi2Ta 2O9 and Sr0.8Bi2.2Ta2O9 thin films on MgO substrate in THz frequency region by THz time-domain spectroscopy. The imaginary parts of the dielectric constant of both the samples show broad peaks in the frequency range 0.5–1.0 THz, which may be due to the soft mode in SBT in this frequency spectrum. The difference in the real part of the dielectric constant of Sr0.8Bi2.2Ta2O9 thin films is small for MHz and THz frequencies. On the other hand, the value of real part of dielectric constant of SrBi2Ta2O9 thin films in THz frequency range is much smaller than that in MHz frequency region, indicating that SrBi2Ta2O9 is not simply displacive ferroelectric material.
Low-Temperature Synthesis and Dielectric Properties of Single-Phase Lead Zirconate Titanate Thin Film with a Nano Particle Seeding Technique
Authors: Tanase Tomokazu , Kobayashi Yoshio , Miwa Takao , Konno Mikio 
Published: April 2011

ABSTRACTThe low temperature synthetic method, which combines chemical solution deposition and nm-seeding technique, was applied to the fabrication of lead zirconate titanate (PZT) thin films. Nano-crystallines of barium strontium titanate (BST) particles were prepared by the hydrolysis reaction of the complex alkoxides. PZT precursor solutions containing the BST particles were spin-coated on Pt/Ti/SiO2/Si substrates to film thickness of 500 − 800 nm at particle concentrations of 0–25.1 mol%, and annealed at various temperatures. Seeding of BST particles prevented the formation of pyrochlore phases, which appeared at temperatures above 400 °C in unseeded PZT films, and crystallized PZT into perovskite structures at 420 °C, which was more than 100 °C below the crystallization temperature of the unseeded PZT films. Measurement of dielectric properties at 1 kHz showed that the 25.1 mol% BST-seeded PZT films annealed at 450 °C had a dielectric constant as high as 300 with a dissipation factor of 0.05. Leakage current density of the film was less than 1×10-6 A/cm2 at applied electric field from 0 to 64 kV/cm.
Low Temperature Dielectric Properties of BST/ZrO2 Multilayer Films
Authors: Sahoo Santosh K. , Agrawal D. C. , Majumder S. B. , Katiyar R. S. , Mohapatra Y. N. 
Published: April 2011

ABSTRACTThin films of Ba1-x SrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and low fatigue. Several approaches have been used to improve the properties of thin films such as doping with aliovalent dopants, graded compositions, and layered structures. We have found that interposing layers of an electronic insulator such as ZrO2 in between BST layers results in a significant reduction in the leakage current. In this paper the low temperature electrical properties of these multilayer structures are reported. The structures consist of alternate layers of Ba0.8Sr0.2TiO3 and ZrO2 deposited by a sol-gel process on platinized Si substrates. The thickness and the number of layers are varied while keeping the total thickness of the film constant. Multiple peaks in the dielectric constant vs temperature plots at all frequencies are observed in the multilayered films. The properties of the multilayer films are a complex function of the number of layers and their thicknesses. A structure with several thin layers of ZrO2 interposed between the BST layers produces smoother plots than a single layer of ZrO2 of same total thickness. This is attributed to more uniform distribution, as determined by XPS, of ZrO2 in the multilayer structure due to smaller diffusion distances.
Microwave Measurements of Ferroelectric Thin Films: Techniques, Error and Limitations
Authors: Petrov Peter Kr. 
Published: April 2011

ABSTRACTThis paper examines the problem of evaluating the microwave properties of thin ferroelectric films patterned as planar capacitors. Two types of microwave measurements of ferroelectric thin films are considered: reflection and resonance type measurements. Algorithms are presented for evaluation of capacitance-permittivity and dielectric loss. Using sensitivity analysis, the error and limitations associated with these measurements are estimated. The end result is a series of formulae that use the network analyser's measurement data to calculate the capacitance-permittivity, the dielectric loss, and the associated error.
Property Design of SrBi2Ta2O9 by Defect Engineering
Authors: Noguchi Yuji , Miyayama Masaru 
Published: April 2011

ABSTRACTDefect engineering is shown to be an effective to design for remanent polarization (Pr) and coercive field (Ec) in SrBi2Ta2O9 (SBT). Cation vacancies and oxygen vacancies are shown to play an essential role in the polarization properties. The ceramic samples were prepared by a solid-state reaction, and high-density ceramics (over 95% of the theoretical density) were used for the measurements of polarization and dielectric properties. High-resolution neutron powder diffraction revealed that trivalent-cation (Bi, rare-earth elements [RE=La, Ce, Pr, Nd, Sm]) substitution induces Sr vacancies in the perovskite blocks for the requirement of charge neutrality. The substitution of La with Sr vacancies (La0.33Sr0.5Bi2Ta2O9) increased 2Pr from 13 μC/cm2 (SBT) to 16 μC/cm2, and the 2Ec value (41 kV/cm) was much smaller than that of SBT (57 kV/cm). Nd-substituted SBT showed the same Pr of La-SBT, while 2Ec (140 kV/cm) of Nd-SBT (x=0.5) was much higher than that of La-SBT. The higher Ec found for Nd-SBT is attributed to partial Nd substitution at the Ta site with the creation of oxygen vacancies. The control of Ec for RE-SBT is discussed in terms of Sr vacancies and oxygen vacancies.
Fabrication of Ru/Bi4−xLaxTi3O12/Ru Ferroelectric Capacitor Structure Using a Ru Film Deposited by Metalorganic Chemical Vapor Deposition
Authors: Furukawa Taisuke , Kuroiwa Takeharu , Fujisaki Yoshihisa , Sato Takehiko , Ishiwara Hiroshi 
Published: April 2011

ABSTRACTA Ru/ Bi 4-xLaxTi 3O12/Ru (Ru/BLT/Ru) capacitor structure with Ru top electrodes deposited by metalorganic chemical vapor deposition (MOCVD) was fabricated. On a Ru film deposited by MOCVD, BLT film was formed by a sol-gel method and crystallized in vacuum. Depositing a conformal Ru film on a BLT/Ru structure by MOCVD, Ru/BLT/Ru stack with smooth and flat surface was successfully formed. Then, ferroelectric Ru/BLT/Ru capacitors were fabricated through a dry etching process. It exhibited both good ferroelectric properties (2Pr =16 μC/cm2) and low leakage current density (J =10−7 A/cm2), suggesting that Ru film deposited by MOCVD showed sufficient properties for the tope electrode of Ru/BLT/Ru structures.
Single- and Multi-target Pulsed Laser Deposition of Thin BSTO films: Preparation, Microstructure and Electrical Properties
Authors: Sarma Kumaravinothan , Petrov Peter Kr. , Alford Neil McN. 
Published: April 2011

ABSTRACTA comparative study of microstructure and electrical properties of BaxSr1-xTiO3 films made by single- and multi-target pulsed laser deposition was carried out. The films were epitaxially grown on both LaAlO3 and MgO substrates. The structural properties of all samples were investigated using X-ray diffraction and Raman spectroscopy. The elemental composition of the samples was investigated using energy dispersive X-ray analysis. For electrical properties examination, a simple capacitor structure was patterned on the film surface. Thin films made using both methods exhibit similar structural and electrical properties; however the samples made by a multi-target method underwent phase transition in a broader temperature region. The results prove the possibility of using the multi-target pulse laser deposition as a more flexible method for engineering thin film stoichometry.
Ferroelectric Films and Multilayers with Ultrahigh Dielectric Constants
Authors: Li Kewen , Zou Kevin , Wang Yanyun , Jiang Hua , Chen Xuesheng 
Published: April 2011

ABSTRACTThis work presents a systematic study of ferroelectric films and multilayers made by a metal-organic chemical liquid deposition method. BaxSr1-xTiO3, Pb(Mg1/3Nb2/3)O3-PbTiO3, and Pb(Zn1/3Nb2/3)O3-PbTiO3 films, as well as multilayers incorporated with these materials have been grown at different conditions. Ultrahigh dielectric constant (∼6700) has been achieved in the PMN/PZN-PT multilayers when the sublayer thickness approached to nanometer scale, where interfaces become dominant. When the sublayer materials with desired Curie temperatures were properly chosen, the temperature dependent dielectric constant of the multilayer structure could be greatly reduced. These nanostructured multilayers may find very important applications where temperature variation is a key concern. Pb doping in BaxSr1-xTiO3 was found very efficient in increasing the dielectric constant and reducing the loss. It is believed that the addition of Pb improved the film density and reduced the grain boundary defects.