bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic Structure and Bonding at the Al-terminated Al(111)/α-Al2O3(0001) Interface: A First Principles Study
Authors: Siegel Donald J. , Hector Louis G. , Adams James B. 
Published: April 2011

AbstractWe have performed ab initio calculations to determine the bonding character of the Al-terminated Al(111)/α-Al2O3(0001) interface. By using an optimized model in which all atomic coordinates were relaxed to their minimum energy positions, we have determined that Al-O bonds constitute the primary interfacial bonding interaction. Our electron localization, Mayer bond order, and Mul- liken population analyses reveal that these bonds are very similar to the cation-anion bonds found in the bulk oxide, and are therefore mainly ionic, with a smaller amount of covalent character. However, there is also evidence of metal-cation bonding across the interface, a result which could be significant to understanding bonding at interfaces with other corundum-like oxides.
Calculations of Perovskite Surface Relaxation
Authors: Heifets E. , Kotominc E.A. , Eglitisc R.I. , Cohen R.E. 
Published: April 2011

AbstractThe (100) and (110) surface relaxations are calculated for SrTiO3 and BaTiO3 perovskite thin films by means of a semi-empirical shell model (SM) for different surface terminations. Our SM results for the (100) surface structure are in good agreement with our present ab initio Hartree-Fock calculations with electron correlation corrections, previous ab initio pseudopotential calculationsand LEED experiments. The surface energy for the Ba-, Sr-, TiO- terminated (110) surfaces is found much larger than that for the (100) one. In contrast, the surface energy for the asymmetric O-termination, where outermost O atoms are strongly on-plane displaced, is the lowest for all (110) terminations and thus the most stable.
Exudation of Silicate Liquid from Polycrystalline Alumina
Authors: Ravishankar N. , Farrer Jeffrey K. , Carter C. Barry 
Published: April 2011

AbstractThe presence of a liquid film at grain boundaries affects the mechanical properties of the material. One of the ways to eliminate the liquid film is to exude it from the grain boundaries to the free surface of the material. The present paper presents results on the exudation of a liquid silicate from grain boundaries in polycrystalline alumina. The results are compared to exudation behavior from bicrystals of alumina. This approach is very useful in understanding the mechanism of the exudation process.
Scaled PLZT Thin Film Capacitors with Excellent Endurance and Retention Performance
Authors: Chu Fan , Fox Glen , Davenport Tom 
Published: April 2011

AbstractThe requirements for future ferroelectric non-volatile memories (FRAM) include lower operating voltages, higher densities and tighter design rules. In order to achieve these requirements the key component of the FRAM device, viz., the PbZrxTi1划xO3 (PZT) thin film capacitor must be scaled dimensionally to obtain reduced film thickness and capacitor area. This paper presents the ferroelectric performance of RF magnetron sputtered PLZT thin films with thickness scaled down to 1000Å. The switching performance of the thickness scaled PLZT thin films meets the requirements of 1.8V FRAM device. Though PLZT ceramic thin films, of which the fatigue is often a concern, are utilized as non-volatile component, excellent fatigue performance was observed. The scaled PLZT thin film capacitors are fatigue free up to 1011 fatigue cycles (E=200kV/cm). The scaled 1000Å PLZT thin films also showed good imprint performance. The opposite-state charge after 10 years baking at 150°C was still above the sensing level. The thickness scaled PZT thin films, showing dramatically improved ferroelectric performance, can be applied to the manufacturing of low voltage FRAM products.
Fatigue in PZT Thin Films
Authors: Shur V. , Nikolaeva E. , Shishkin E. , Baturin I. , Bolten D. , Lohse O. , Waser R. 
Published: April 2011

AbstractWe have used the new approach to fatigue phenomenon for analysis of the switching current and C-V characteristic evolution during cycling in PZT thin films. It was shown that in accordance with theoretical predictions the rejuvenation stage precedes the fatigue one. We have demonstrated that fatigue behavior corresponds to the spreading of the internal bias field distribution function during ac switching.
Electrical Characteristics of Chemical Solution Deposited Nd3+ Doped PZT (53/47) Thin Films in Planar Electrode Configuration
Authors: Majumder S.B. , Perez B. , Roy B. , Martinez A. , Katiyar R.S. 
Published: April 2011

AbstractElectrical characteristics of ferroelectric thin films in planar electrode configuration are important to characterize these materials for their applications in micro electro mechanical (MEM) and tunable microwave devices. In the present work we have prepared polycrystalline Pb1划3x/2Ndx(Zr0.53Ti0.47)O3 (x = 0.0 to 10.0 at %) thin films on platinized silicon substrate by chemical solution deposition (CSD) technique. The films were characterized in terms of their dielectric and ferroelectric properties by depositing planar interdigital finger electrodes on the surface of the films by electron beam lithography. The capacitance and loss tangent of undoped and 4 at % Nd doped PZT films measured at 100 kHz were found to be 138 pF, 0.033 and 95 pF, 0.019 respectively. Saturated hysteresis loops were obtained in undoped PZT film by applying 100 V across 10 μm electrode separation. Nd doped PZT films on the other hand, electrically shorted at comparatively lower voltage. The electrical characteristics of these films are correlated with their phase formation behavior and microstructural features.
High Frequency Thin Film Acoustic Ferroelectric Resonators
Authors: Kirby Paul , Su Qing-Xin , Komuro Eiju , Imura Masaaki , Zhang Qi , Whatmore Roger 
Published: April 2011

AbstractBoth ZnO and PZT Thin Film Bulk Acoustic Resonator filters were fabricated, tested and modeled in this study. The development of an accurate Mason model allows the effect of particular parasitic components on the microwave s-parameters in the region of the series and parallel resonances to be identified. The parasitic components that limit the performance of our ZnO and PbZr0.3Ti0.7O3 Thin Film Bulk Acoustic Resonator filters are analysed. From an analysis of PbZr0.3Ti0.7O3 Thin Film Bulk Acoustic Resonator measurements values for the longitudinal acoustic velocity and electromechanical coupling coefficient can be derived. Measured PbZr0.3Ti0.7O3 Thin Film Bulk Acoustic Resonator filter responses confirm that the larger electromechanical coupling coefficients in this material compared to ZnO give wider filter band-widths.
Improvement of Retention Property of YMnO3/Y2O3/Si MFIS Capacitor
Authors: Daisuke Ito Norifumi Fujimura , Kakuno Kousuke , Ito Taichiro 
Published: April 2011

AbstractWe have been proposing YMnO3 with low remanent polarization and permittivity as a ferroelectric gate transistor, and reported that c-oriented YMnO3 films were obtained on (111)Si with (111) oriented Y2O3 buffer layer. The ferroelectricity was confirmed by pulsed C-V measurement. However, the retention property was not satisfied because of its poor crystallinity. To improve the crystallinity of YMnO3 films, deposition conditions of Pulsed Laser Deposition (PLD) were optimized. The laser power, oxygen pressure and introducing Ozone gas are effective for maintaining the stoichiometry during the deposition. Improvement of the crystallinity of the YMnO3 film makes the retention property better. We also demonstrate the use of epitaxially grown Y2O3 buffer layer to improve the crystallinity of the YMnO3 films.
Direct Comparison of Structural and Electrical Properties of Epitaxial (001)-, (116)-, and (103)-Oriented SrBi2Ta2O9 Thin Films on SrTiO3 and Silicon Substrates
Authors: Lee H. N. , Pignolet A. , Senz S. , Harnagea C. , Hesse D. 
Published: April 2011

AbstractAnisotropies of the properties of the bismuth-layered perovskite SrBi2Ta2O9 (SBT) have been investigated using epitaxial thin films grown by pulsed laser deposition both on conducting Nb-doped SrTiO3 (STO) single crystal substrates and on Si(100) substrates. It has been found that the three-dimensional epitaxy relationship SBT(001)∥STO(001); SBT [110] ∥STO[100] can be applied to all SBT thin films on STO substrates of (001), (011), and (111) orientations. An about 1.7 times larger remanent polarization was obtained in (103)-oriented SBT films than in that of (116) orientation, while the (001)-oriented SBT films revealed no ferroelectricity along their c-axis. Non-c-axis-oriented SBT films with a well-defined (116) orientation were also grown on silicon substrates for the first time. They were deposited on Si(100) covered with a conducting SrRuO3 (110) bottom electrode on a YSZ(100) buffer layer.
Nanometer Scale Domain Measurement of Ferroelectric Thin Films Using Scanning Nonlinear Dielectric Microscopy
Authors: Odagawa Hiroyuki , Matsuura Kaori , Cho Yasuo 
Published: April 2011

AbstractA very high-resolution scanning nonlinear dielectric microscope with nanometer resolution was developed for the observation of ferroelectric polarization. We demonstrate that the resolution of the microscope is of a sub-nanometer order by measurement of domains in PZT and SBT thin films. The experimental result shows that nano-sized 180° c-c ferroelectric domain with the width of 1.5 nm for PZT thin film are observed. The result also shows that the resolution of the microscope is less than 0.5 nm for the PZT thin film.
Lattice Vibrational Properties of SrBi2Ta2O9
Authors: Liu Ran , Han Pengdi 
Published: April 2011

AbstractSrBi2Ta2O9 is one of the layered perovskite ferroelectrics with excellent fatigue resistance and thus has gained great interest of semiconductor industries recently in non-volatile ferroelectric random access memory (FERAM) applications. The understanding of the lattice vibrational properties of this material can provide crucial information on its structure and dielectric behavior. In this work, we carried out Raman spectroscopy study of thin film, powder and single crystal SrBi2Ta2O9. At temperatures above the Curie temperature, all 12 Raman modes expected from the tetragonal (I4/mmm) structure have been observed and assigned to the 4 A1g, 6 Eg and 2 B1g modes based the polarized Raman spectra from the single crystal samples. At lower temperature, the Raman spectra have revealed all 22 A1 modes, but only 3 out of the 20 A2 modes and 5 out of the 42 B1/B2 modes were observed in the ferroelectric phase (A21am). The soft mode was found to be of A1 symmetry and appearing only when light polarization lay in the ab-plane.
Strain-Induced Elevation of the Spontaneous Polarization in BaTiO3 Thin Films
Authors: Tian W. , Haeni J. H. , Schlom D. G. , Pan X. Q. 
Published: April 2011

AbstractA manmade ferroelectric-paraelectric heterostructure, a BaTiO3 / SrTiO3 superlattice, was studied to explore the effect of strain on ferroelectricity. An atomically abrupt BaTiO3 / SrTiO3 superlattice was grown on a (001) SrTiO3 substrate by reactive molecular beam epitaxy. Both BaTiO3 and SrTiO3 layers were grown with their individual thicknesses less than the critical thickness for the formation of interfacial misfit dislocations, leaving the entire superlattice fully coherent with the substrate. This resulted in a uniformly and highly strained BaTiO3 layer to study the effect of strain on ferroelectricity. Quantitative high-resolution transmission electron microscopy was employed to examine the atomic positions of cations and anions in the strained BaTiO3 layers. It was found that the relative static displacement of cations (Ti4+, Ba2+) to anions (O2−) is larger than that of bulk BaTiO3. Our observation thus illustrates the strain-induced elevation of spontaneous polarization in BaTiO3 thin films.
Orientation Selection in Sol-Gel Derived PZT Thin Films
Authors: Norga G. J. , Fé Laura 
Published: April 2011

AbstractMotivated by the growing impact of PZT film orientation on ferroelectric film properties as film thickness is scaled down, we present basic studies on orientation selection in sol-gel derived PZT films, using pre-annealed Pt/Ti electrode layers as a model electrode system. FTIR was used to study, on a real temperature scale, chemical reactions in the films during the initial thermal steps prior to crystallization. We found that the chemical structure of the pyrolyzed film has a much larger impact on orientation selection than has previously been realized. In addition to pyrolysis conditions, the ambient used for the crystallization step was found to play a crucial role in orientation selection. As film thickness decreases, excessive oxygen incorporation in the films is seen to result in the loss of the preferential (111) texture when crystallization is performed in air. By performing crystallizations in N2, 40 nm thick PZT films with a strongly preferential (111) orientation could be obtained.
Electrophoretic Deposition of Barium Strontium Titanate Functionally Graded Thick Film Composites for Electronically Scanning Antennas
Authors: Gersten Bonnie , Synowczynski Jennifer 
Published: April 2011

ABSTRACTThe composition 40 wt% Ba0.55Sr0.45TiO3 (BST) – 60 wt% MgO bulk material was recently found to be a promising candidate as a low loss, tunable material for electronically scanning antennas (ESA). However, due to the high permittivity of the BST-MgO composite impedance mismatch within the antenna could be a source of loss. Electrophoretic deposition (EPD) could be used as a processing tool to develop functionally graded structures tailored to reduce the impedance mismatch without a reduction in the tunability. In addition, EPD could be used in thin or thick films to decrease the required biasing fields. In this study, EPD was used as a method for deposit thick films of BST functionally graded composites. The concentration of the suspension, solvent type, mixed solvent concentrations, bias field, time, particle size of powders and distance between electrodes were studied to control the deposition yield and thickness. SEM or calipers were used to measure deposit thickness. The relative weight ratio of BST to MgO in the suspension was compared to the final structure as measured by EDS.
Connection between Near Millimeter Range Dielectric Loss and High Frequency Acoustic Attenuation
Authors: Garin Boris M. , Ivanov Sergey N. , Khazanov Efim N. , Nikitin Ivan P. 
Published: April 2011

ABSTRACTA series of crystalline isomorphic solid solutions of Yttrium-Lutetium Aluminum Garnets (Y1−cLuc)3Al5O12 (c = 0 – 1) has been studied. The measurements of dielectric loss (DL) tangent tgδ has been performed at electromagnetic wavelengths 1 – 0.6 mm and temperature T = 300 K. The results obtained has been compared with longitudinal acoustic waves (AW) attenuation data for frequencies f = 1 – 9.4 GHz, T = 4.2 – 300 K and with theory. The correlation between the DL and the AW attenuation is observed. The dependencies of DL (at T = 300 K) and AW attenuation (at T > 77 K) on concentration c are qualitatively identical in the whole interval c = 0 – 1. From comparison with theory it follows that the observed DL is due to the two-phonon intrinsic lattice loss. It is caused by the lattice anharmonicity as well as the AW attenuation at not too low temperatures. Also the prediction for concentration dependence of DL at very low temperatures is discussed that follows from comparison with the results of “heat pulse” propagation experiments for the same samples at T = 2 K and theory.
Tunability in Ba1–xSrxTiO3-based Ferroelectrics
Authors: Potrepka Daniel M. , Tidrow Steven C. , Tauber Arthur 
Published: April 2011

ABSTRACTFerroelectrics are presently of interest for phase shifters, filters, and true time delay devices. Voltage tunable paraelectrics have the potential to lower device cost and reduce power consumption compared with presently available devices. In order to improve device performance to acceptable levels, materials must have high tunability, low dielectric constant, low loss tangent, and low leakage current. Using existing predictive techniques, compositions of Ba0.6Sr0.4TiO3-based ferroelectrics with charge-compensated substitutions for Ti4+ were synthesized. Results of capacitance measurements are used to obtain dielectric constant and tunability in the paraelectric (T > TC) regime. The relevance to device requirements is discussed. Results for substituted samples are compared to those for (unsubstituted) Ba0.6Sr0.4TiO3. Discussion of the impact of the results on predictive techniques for tunability is addressed.
Resonating Microelectromechanical Structures for Metrology
Authors: Allen A. M. , Johnson G. C. 
Published: April 2011

ABSTRACTA method for determining geometric process errors in MEMS devices from the resonant fre- quencies of simple structures is presented. The ability to accurately determine the as-built ge- ometry of MEMS devices is important given the magnitude of the geometric uncertainty relative to the dimensions of these devices. As MEMS become smaller, the need for reliable metrology becomes even more important. The method presented here provides a way to determine the etch offset (the difference between the design width of a planar feature and the as-built width), the average angle of the side-walls and the compliance of the support of the structure. An important feature of the approach presented is that by using frequency ratios for various structural modes, neither the elastic modulus nor the mass density of the film need be known.
Novel Chemistry for Surface Engineering in Mems
Authors: Zhu X.-Y. , Jun Y. , Boiadjiev V. , Major R. , Kim H. I. , Houston J. E. 
Published: April 2011

ABSTRACTIt is well recognized that controlling surface forces is one of the key issues in the design, fabrication, and operation of microelectromechanical systems (MEMS). In this report we present a novel strategy for the efficient assembly of organic monolayers onto silicon surfaces to control surface energy. This is achieved by the reaction between an alcohol functional group and a chlorinated Si surface. The resulting molecular monolayers are thermally and chemically stable. Surface adhesion energy on silicon is reduced by a factor of 40 by the monolayer coating and friction coefficient of the coated surface is only 0.013. The coatings are successfully demonstrated in adhesion reduction in a model MEMS structure: cantilever beam array (CBA). Polycrystalline beams with length up to 1.5 mm can be released.
Structural and Micromechanical Assessment of Electrochemically Grown Metal Layers for Si Magnetic Microactuators
Authors: Martinez Susanna , Yaakoubi Nourdin , Serre Christophe , Pérez-Rodríguez Alejandro , Morante Joan Ramon , Díez-Pérez Ismael , Gorostiza Pau , Esteve Jaume 
Published: April 2011

ABSTRACTThe electrochemical deposition of Cu metal layers for Si based microactuator devices is investigated as a function of the substrate structure. For the direct deposition of Cu onto Si, a two step process involving pre-deposition of an intermediate layer under alkaline conditions has been developed. This has allowed the optimization of the process in terms of film adherence and thickness. On the other hand, for processes involving the use of dielectric sacrificial layers, the electrochemical growth of the Cu film requires a metallic seed layer. In this case, the growth of Cu onto Au coated surfaces has been investigated, and the process has been applied to the development of test microactuator structures based on the integration of Cu coils onto Si micromachined devices. The fabrication of these devices demonstrates the full compatibility of Electrochemical processes with Si standard micromachining technologies.
Temperature and Doping Dependency of Piezoresistivity in p-type Silicon
Authors: Lund Eivind , Finstad Terje G. 
Published: April 2011

ABSTRACTWe have performed new measurements of the temperature and doping dependency of the piezoresistive effect in p-type silicon. Piezoresistivity is one of the most common sensing principles of micro-electro-mechanical-systems (MEMS). Our measurements are performed in a specially designed setup based on the well-known 4 point bending technique. The samples are beams of full wafer thickness. To minimize leakage currents and to obtain uniform doping profiles, we have used SIMOX (Separation by IMplantation of OXygen) substrates with resistors defined in an epitaxial layer. Spreading resistance measurements show that the doping profiles are uniform with depth, while measurements of leakage current versus temperature indicate low leakage current. In this paper we present results for the doping concentration range from 1×1017 – 1×1020 cm−3 and the temperature range from –30 to 150 degrees Celsius. The results show a doping dependency of piezoresistivity well described by the current models. The measurements of the temperature dependency of the coefficients of piezoresistivity are compared to a linear model with a negative temperature coefficient whose absolute value decreases with increasing doping.
Optical Manipulation of Inorganic and Organic Objects in Soft Microfluidic Devices
Authors: Ozkan Cengiz S. , Ata Erhan , Ozkan Mihrimah , Esener Sadik C. 
Published: April 2011

ABSTRACTWe describe a technique for trapping and manipulation of inorganic and organic objects in microfluidic channels, based on photonic momentum transfer using an optical tweezers arrangement. Microfluidic devices have been fabricated by polydimethylsiloxane (PDMS) elastomer molding of patterns lithographically defined on a thick negative photoresist. Polystyrene microspheres dispersed in water were transferred into the fluidic channels using a syringe pump. Microspheres and live biological cells are trapped and redirected by optical manipulation within the fluidic channels. Optical trapping and patterning will have applications in creation of active cellular arrays for cell biology research, tissue engineering, cell sorting and drug discovery.
Simple and Low Cost Patterning Process for Sputtered Pb(Zr,Ti)O3 Thin Films and Electrodes for Membrane-Based Microsystems Applications
Authors: Millon Cyril , Malhaire Christophe , Defaÿ Emmanuel , Barbier Daniel 
Published: April 2011

ABSTRACTMicromachined silicon membranes actuated by a piezoelectric thin film are of great interest for microfluidic or ultrasonic applications. In this paper, we present a simple and low cost patterning process for sputtered Ti and Pt electrodes and Pb(Zr,Ti)O3 thin films using lift-off and a wet HCl etching methods respectively. We have showed by finite element analysis the incentive to pattern electrodes in order to get higher actuation performances. Moreover, in order to reduce the stress on the diaphragm, the PZT film has been also patterned. We propose an optimized flow chart taking into account the different material properties in the multi-layer stack constituting the actuator and the need of a PZT crystallization annealing. To show the influence of the actuator layout, finite element models of a 20μm thick, 3 × 3 mm2 silicon membrane with variable electrode design, actuated by a 1μm PZT (10 V bias) thin film have been developed. We found a maximum deflection for a 1.7 mm side length square electrode located at the membrane center. Sputtering was achieved on a non-heated silicon substrate, in pure Argon, using a stoichiometric PZT target. The metallic electrodes have been structured by standard lift- off technique. Different concentrations of HCl [4 % - 35 %] with temperature up to 90°C have been tested for PZT patterning. Well defined PZT microstructures were better achieved by wet etching of unannealed PZT film on SiO2 or Pt (HCl 35%, room temperature). The etching rate was 40 nm.s−1. The presence of the perovskyte phase in the PZT films after a 700°C, 30 s RTA in air, has been checked by X-ray measurements. Finally, the silicon membranes have been realized by anisotropic chemical etching in an aqueous KOH (40 %, 60°C) solution. Membrane deflection under low bias have been successfully tested.