bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ferroelectric and Ferromagnetic Properties of BiFeO3 Thin Films Deposited by Pulsed Laser Deposition
Authors: Yun Kwi-Young , Noda Minoru , Okuyama Masanori , Saeki Hiromasa , Tabata Hitoshi 
Published: April 2011

ABSTRACTBiFeO3 thin film has been prepared on Pt/TiO2/SiO2/Si substrate at a temperature as low as 450°C by pulsed-laser deposition. The BiFeO3 thin film is perovskite single-phase, while any nonperovskite phase, such as orthorhombic Bi2Fe4O9, is not included. Dielectric constant of the film is 87, dielectric loss is 0.03, and leakage current density is low. The coexistence of ferroelectricity and ferromagnetism has been confirmed by means of the P-E and M-H hysteresis characteristics. The BiFeO3 thin film shows a well-saturated hysteresis loop with twice the remanent polarization 2Pr = 54 μC/cm2 and coercive field 2Ec = 100 kV/cm for a maximum applied electric field of 100 kV/cm, and also shows a saturated weak ferromagnetic hysteresis loop, as well as a small remanent magnetization with 2Mr = 0.6 emu/cm3 and 2 Hc = 200 Oe for a maximum magnetic field of 10 kOe at room temperature.
First-principles study of the electronic structure of Pb(ZrTiNb)O3 (PZTN) systems
Authors: Miyazawa Hiromu , Higuchi Takamitsu , Aoyama Taku , Kijima Takeshi , Natori Eiji , Shimoda Tatsuya , Oguchi Tamio 
Published: April 2011

ABSTRACTUsing first principles calculations, we have investigated the electronic structure of Pb(ZrTiNb)O3 (PZTN), a system with a low leakage current and high reliability in thin films. We proposed that in PZTN, the oxygen vacancy is suppressed due to the addition of a Nb atom at the B site and that this change prevents a bandgap narrowing which would enhance the leakage current. The oxygen vacancy in the perovskite structure reduces the bandgap because it lowers the d orbital energy of the nearest-neighbor transition metal through the Madelung potential; this bandgap narrowing induces the leakage current in conventional Pb(ZrTi)O3 (PZT) systems with the Shottky type Pb-O deficit. In contrast, the PZTN systems, which also have the Pb deficit but lack the oxygen vacancy, can maintain the bandgap, and attain a low leakage current.
Effect of Cationic Substitution on Raman Spectra of SrBi2Ta2O9Ceramics and Thin Films
Authors: Perez W. , Das R. R. , Dobal P. S. , Yuzyuk Y. I. , Bhattacharya P. , Katiyar R. S. 
Published: April 2011

ABSTRACTIn the present work micro-Raman spectroscopy has been used to understand the lattice dynamics of cation substituted SBT ceramics and thin films. Different concentrations of Ca and V were introduced into SBT lattices. Incorporation of Ca ion at Sr-site was confirmed by decrease in the lattice parameters calculated from x-ray diffraction data. The lowest Raman modes at 27 cm-1and 58 cm-1showed upward shift with increasing Ca concentration and was attributed to the lower mass and lower ionic radii of Ca. The temperature dependant Raman studies revealed the increase of the phase transition temperature with increased Ca content, and was attributed to the decrease in tolerance factor. Substitution of smaller cation at Sr site in SBT compound has increased lattice mismatch between SrO and TaO2planes inside the stable perovskite unit of SrTa2O7which has pronounced influence on ferroelectric properties of SBT. Substitution of vanadium at Ta-site of SBT did not influence the low frequency Raman modes of SBT. However, it showed a pronounced influence on the O-Ta-O stretching modes by splitting the mode frequency at 810 cm-1. The transition temperature of SBT was reduced with increasing vanadium contents.
Effect of Thermal Strain on Domain Fraction in a-/b-axis-oriented Epitaxial Bi4Ti3O12 Films
Authors: Watanabe Takayuki , Morioka Hitoshi , Okamoto Shoji , Takahashi Masatake , Noguchi Yuji , Miyayama Masaru , Funakubo Hiroshi 
Published: April 2011

ABSTRACTa-/b-axis-oriented epitaxial Bi4Ti3O12 and neodymium-substituted Bi4Ti3O12 films with a different a-domain fraction, V(100)/[V(100)+V(010)], were grown by metalorganic chemical vapor deposition above the phase transition temperature. It was demonstrated that the saturation polarization observed for the a-/b-axis-oriented film is proportional to the a-domain fraction estimated by x-ray diffraction. The liner relationship passing through the origin revealed that the 90° domain switching by an external electric field hardly occurred. The extrapolation gave spontaneous polarization of 58 μC/cm2 for a pure a-axis-oriented (Bi3.5Nd0.5)Ti3O12 film. The domain fraction was investigated as a function of thermal strain originated from a difference in thermal expansion coefficient between the film and substrates. The domain fraction of the films changed with the thermal strain along the in-plane [010] in tetragonal a-axis-oriented films as well as epitaxially grown tetragonal Pb(Zr,Ti)O3 films.
Thickness and Strain Effects on RF/Microwave Properties of BST Thin Films on NdGaO3 Substrates
Authors: Simon William Kurt , Koray Akdogan E. , Bellotti Jeffery , Safari Ahmad 
Published: April 2011

ABSTRACTBa0.60Sr0.40TiO3 thin films were deposited on <100> oriented NdGaO3 substrates by pulsed-laser deposition. Film thickness ranged from 20 nm to 800 nm. Microstructural features, as evaluated with AFM and FESEM, have exhibited high quality thickness dependent topography. X-ray analyses have shown consistently <110> textured films of high crystallinity. Permittivity, Q-factor, and tunability, were investigated using interdigitated capacitors in the 0.1–20 GHz range. Effect of film thickness on dielectric properties and tunability in polycrystalline <110> textured films exhibited strong thickness dependence in their elasto-dielectric properties. Tunability up to 45% was observed at moderate field levels (∼ 7 MV/m), while the Q-factors remained ≤40.
Growth of epitaxial tetragonal Pb(Zr,Ti)O3thin films with 100% polar-axis-orientation and their electrical properties
Authors: Morioka Hitoshi , Yokoyama Shintaro , Oikawa Takahiro , Saito Keisuke , Funakubo Hiroshi 
Published: April 2011

ABSTRACTPb(ZrxTi1-x)O3(PZT) thin films with the various Zr/(Zr+Ti) ratios and the film thickness of 50 and 250 nm were epitaxiallly grown on (100)cSrRuO3//(100)SrTiO3substrates by metalorganic chemical vapor deposition at 540 °C. 50 nm-thick tetragonal PZT films consistd of 100%c-axis-orientation for the Zr/(Zr+Ti) ratio ranging from 0.13 to 0.56, while 250 nm-thick tetragonal ones consistd of about 70%c-axis-orientation for the range from 0.19 to 0.45. On the other hand, 50 and 250 nm-thick films composed rhombohedral single phase for the Zr/(Zr+Ti) ratio above 0.56 and 0.60, respectively. Mixture region of tetragonal and rhombohedral phases was observed from 0.45 to 0.60 for 250 nm-thick films, but was not for 50 nm-thick ones. Remanent polarization monotonously decreased with increasing the Zr/(Zr+Ti) ratio for 50 nm-thick films in tetragonal PZT films. These results show that Ti rich tetragonal PZT thin films have large spontaneous polarization with good square-shape hysteresis loops and are applicable for the high-density capacitor-type ferroelectric random access memories.
Enhancing Tunability and Decreasing Temperature Sensitivity
Authors: Tidrow S. C. , Tauber A. , Potrepka D. M. , Crowne F. , Rod B. 
Published: April 2011

ABSTRACTThe employment of judicious substitution on B-sites in the perovskite oxide, BaTiO3, has yielded materials suitable for relatively temperature insensitive electric field tunable microwave devices. The properties, single-phase cubic perovskites with tunabilities as large as 30% at 1 V/μm and room temperature that possess low temperature coefficient of dielectric constant and tunability over the majority of the military specified temperature range, -55 to 125 °C, have been achieved in the charge compensated system Ba1-xSrxTi1–2yCyDyO3 where C is Ho, Er, Tm, Lu, Sc, Y, In and D is Ta, Sb with 0 ≤ X ≤ 0.2, and 0 < y ≤ 0.10.
Bi-Directional Motion Achieved with a Surface Micromachined Electrothermal MEMS Microengine
Authors: Kolesar Edward , Jayachandran Alfred , Odom William , Ruff Matthew , McAllister Justin , Ko Simon , Howard Jeffrey , Allen Peter , Wilks Richard , Wilken Josh , Boydston Noah , Bosch Jorge 
Published: April 2011

ABSTRACTThis research is focused on the design and experimental characterization of an electrothermal microengine that is capable of bi-directional motion. The microengine has been operated to control the position a linear shuttle and rotate a set of gears.
Microstructure and Magnetostriction of Rapidly-solidified Fe-Ga System Alloy
Authors: Okazaki Teiko , Furuya Yasubumi , Saito Chihiro , Matsuzaki Takashi , Watanabe Tadao , Wuttig Manfred 
Published: April 2011

ABSTRACTRapid-solidification method was applied to make Fe-15at%Ga and Fe-17at%Ga ribbons of 100 μm thickness. These ribbons have large magnetostriction of 270 ppm, where the coercive force exhibits a maximum value. The phenomenon is related to special metallic texture, that is, the ribbon has strongly [001]-oriented textured fine columnar microstructure with grain size of 2∼5 μm. The ribbon has little-hysteresis loop of magnetostriction and a good ductility (i.e., full bending is possible). Rapid-solidified Fe-Ga alloy has a promising possibility as a new magnetic-induced sensor/actuator material.
Accelerated Reliability Test Inputs in Analyzing the Device Response of MgZnO Based UV Detector
Authors: Hullavarad S.S. , Takeuchi I. , Berger J. , Dhar S. , Chang K.S. , Venkatesan T. , Loughran T.C. , Vispute R.D. , Yedave S.N. 
Published: April 2011

ABSTRACTIn this paper we present the accelerated reliability testing of MgZnO based UV detectors. The UV detectors are fabricated on glass, quartz and sapphire substrates by Pulsed Laser Deposition (PLD) technique. The films are highly oriented and show sharp transmission at 350nm and 330nm for Mg composition of 10% and 20% in ZnO, respectively. The device response has been studied and life expectancy of the devices has been estimated from the accelerated tests.
A Large Grain Polycrystalline Silicon Film for Resistive Bolometers
Authors: Kim Tae-Sik , Lee Hee Chul 
Published: April 2011

ABSTRACTLarge grain polycrystalline silicon films as a sensing material for infrared bolometers have been proposed and investigated. Using a seed selection through ion channeling technique, we have successfully increased the average grain size of polysilicon films up to 1670Å. The achieved TCR value at 20°C and grain boundary defect density of the film are found to be as high as -2.46%/K for a resistivity of 30Ωcm and to be about 1.752×1012/cm2, respectively. From the measurement of noise characteristics of the film, the value of k, 1/f noise parameter, is calculated to be 1.35×10-9. As a result, the estimated detectivity is found to be 5.6×108cmHz1/2/W.
Combinatorial Thin Film Synthesis of NiMnAl Magnetic Shape Memory Alloys Using MBE Technique
Authors: Hassdorf R. , Feydt J. , Thienhaus S. , Borowski R. , Boese M. , Walther T. , Moske M. 
Published: April 2011

ABSTRACTComposition spreads close to the Heusler alloy Ni2MnAl were grown onto 4-inch wafer substrates using molecular beam epitaxy. Compositional variations of up to 10 at.% relative to each constituent enable a direct comparison of the chemical-structural relationship with respect to martensitic transformation and to magnetic ordering as well as an efficient identification of the emerging phase stability regions. In this study, we set the primary focus on the structural aspects of the transformation behavior as observed by X-ray microdiffraction in combination with a specially designed heating stage. Notably, cross-sectional HRTEM imaging of the respective composition areas reveals a laminated two-phase martensitic structure inside the single grains, identified as a sequence of 2M and 14M variants. Stress relief upon transformation as observed by mechanical stress measurements reaches to 400 MPa depending on the composition. Magnetization measurements so far indicate field-induced ordering to occur at low temperatures, here, below 50 K which is assumed to be closely related to a high degree of structural disorder on the Mn-Al sublattice. Single-crystal thin films were realized by means of an epitaxial relationship to MgO (001).
Synthesis and characterization of Ca1-X SrxCu3Ti4O12 thin films for dielectric applications
Authors: Guzman R. , Tomar M.S. , Melgarejo R.E. 
Published: April 2011

ABSTRACTThere is a great deal of interest in CaCu3Ti4O12 system for dielectric applications. We have studied Ca1-xSrxCu3Ti4O12 system for different compositions. The material is synthesized by sol-gel chemical solution route and thin films were deposited by spin coating. Thin films were investigated by x-ray diffraction and Raman spectroscopy for structural properties. These results indicate a solid solution for the compositions x = 0.00 to 0.80. The SEM micrographs shows the uniform films at 800° C, but the dielectric response of Ca1-xSrxCu3Ti4O12 (x = 0.00) shows the dielectric constant value below 200.
Modified BiFeO3-PbTiO3 Morphotropic Phase Boundary (MPB) Piezoelectric Ceramics for High Temperature and High Power Applications
Authors: Cheng JinRong , Eric Cross L. 
Published: April 2011

ABSTRACTBiFeO3-PbTiO3 (BF-PT) crystalline solutions have been modified by La3+, Ga3+ and Ba2+ substituent. The modified BF-PT had morphotropic phase boundary (MPB), at which the ferroelectric rhombohedral phase transferred to the tetragonal symmetry. The piezoelectric properties at the MPB were strongly depended on different substituents. The modified BF-PT system showed the insulation resistivity up to 1012 ω·cm at room temperature. Lanthanum played a critical role making BF-PT softer to be poled to the piezoelectric state. Ga provided BF-PT additional polarization and breakdown strength with La substituent. In the system with La3+, Ga3+ and Ba3+ simultaneously, addition of Ba enhanced dielectric and piezoelectric activity. It was flexible to tailor BF-PT by using different substituents. In the vicinity of MPB, the Curie temperature Tc was above 385°C of BF-PT for La <10 at%, whereas the d33 constant was as high as 295 pC/N for one with La of 20 at%. The modified BF-PT revealed comparable performances to conventional Pb(Zr,Ti)O3 (PZT) ceramics, but in significantly lead reduced forms.
Nanoscale Ferroelectric Properties of PZN-PT Single Crystals Studied by Scanning Force Microscopy
Authors: Bdikin I. K. , Shvartsman V. V. , Kholkin A. L. 
Published: April 2011

ABSTRACTHigh-resolution domain studies were performed in Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 (PZN-PT) single crystals via piezoresponse force microscopy (PFM). Irregular domain patterns with the typical sizes of 20–100 nm were observed on the (001)-oriented surfaces of unpoled samples. On the contrary, (111) crystal cuts exhibited normal micron-sized regular domains with the domain boundaries directed along allowed crystallographic planes. The existence of nanodomains in (100)-oriented crystals was tentatively attributed to the relaxor nature of PZN-PT where small polar clusters were predicted to exist upon zero-field cooling. These nanodomains were considered as the nuclei of the opposite polarization state that ease the switching process for this particular crystal cut. Local piezoelectric hysteresis was also performed by PFM on the nanometer scale. Similar switching behavior of (111)- and (100)-oriented PZN-PT crystals suggests that their superior piezoelectric properties can be related to the domain wall motion rather than to the perovskite lattice itself.
Sterilizing Properties of Carbon Nanotube Composites
Authors: Narayan Roger J. 
Published: April 2011

ABSTRACTHydrogen-free carbon nanotube composites have been created that possess unusual free radical generation properties. These films have the ability to nonspecifically kill bacterial cells and can be used to sterilize a surface. These composites have been formed by simultaneous pulsed laser ablation of carbon and bombardment of nitrogen ions generated by a Kaufman ion source at high temperatures (600- 700°C). The results suggest the creation of a new form of carbon that is predominantly trigonally-coordinated, with small fractions of carbon-nitrogen bonds. TEM studies allow us to conclude that the material consists of sp2-bonded ribbons wrapped approximately +/-15° normal to the surface. Plan-view high resolution TEM specimens demonstrate layers with curvature similar to that seen in multiwalled nanotube structures. In addition, the interlayer order extends to approximately 15–30 nm. These novel structures result from the use of energetic ions, which create nonequilibrium conditions that alter the growth mode of graphitic planes. In vitro testing revealed significant antimicrobial activity against Staphylococcus aureus bacteria. Possible applications include use on the functional surfaces of dialysis equipment, scalpels, and other sterile equipment.
Stability of Nitrogen and Hydrogen in High-k Dielectrics
Authors: Bastos K.P. , Pezzi R.P. , Miotti L. , Soares G.V. , Driemeier C. , Morais J. , Baumvol I.J.R. 
Published: April 2011

ABSTRACTWe report here on atomic transport, thermal stability, and chemical evolution of HfSiO, HfSiN, and AlON films on Si(001), aiming at investigating the atomic scale behaviour of the involved chemical species, N and H in particular, when the films are submitted to usual thermal processing steps in inert and oxidizing atmospheres. The films were characterized by nuclear reaction analyses in resonant and non-resonant regions of the cross-section curves, X-ray photoelectron spectroscopy, and low energy ion scattering. The HfSiN/Si structure was shown to be more resistant to oxygen diffusion than HfSiO/Si, although the amounts of O incorporated in HfSiN/Si are larger than in HfSiO/Si. The main channel of oxygen incorporation is atomic exchange with nitrogen or oxygen atoms. HfSiN film on Si incorporate more hydrogen (or deuterium) and in more stable configurations than HfSiO/Si. Nitrogen incorporation into AlON films on Si renders this structure more stable against thermal annealing in vacuum and/or oxidizing atmospheres than Al2O3/Si.
Crystallinity and Wet Etch Behavior of HfO2 Films Grown by MOCVD
Authors: Saenger Katherine L. , Cabral Cyril , Jamison Paul C. , Preisler Edward , Kellock Andrew J. 
Published: April 2011

ABSTRACTThe crystallinity and wet etching behaviors of ultrathin (<10 nm) HfO2 films grown by metal organic chemical vapor deposition (MOCVD) were examined as a function of deposition temperature, film thickness, and post-deposition annealing. Films 3 nm in thickness deposited at 400 or 500 °C were amorphous as-deposited and slowly etchable in aqueous HF; after annealing at 700 °C, the same films showed some nanocrystallinity and were impervious to HF. However, thicker films grown under the same conditions showed significant crystallinity and were impervious to HF even as-deposited. These observations, in combination with measurements on various samples etched back by an Ar+ ion damage/wet etch process, suggest a film structure comprising an initially amorphous near-interface region capped with a HF-resistant crystalline upper layer. It was found that the initially amorphous near-interface region (the bottom 1–3 nm) of films grown at 500 °C can be induced to at least partially crystallize as the upper part of the film starts becoming crystalline as-deposited, but that this near-interface region remains at least partially amorphous after annealing at 700°C.
Optical and Dielectric Properties of Eu- and Y-Polytantalate Thin Films
Authors: Vasilyev Vladimir , Drehman Alvin , Dauplaise Helen , Bouthillette Lionel , Volinsky Alex 
Published: April 2011

ABSTRACTDue to their highly efficient photo-luminescent (PL) characteristics, the physical properties of rare-earth polytantalates, RETa7O19(RE=Eu and Y) were further studied. AFM, SEM, HRTEM, x-ray reflectometry, spectroscopic ellipsometry and standard dielectric testing were used to determine film thickness, roughness, index of refraction, band-gap, dielectric constant, leakage current and breakdown field for as-deposited (amorphous) and post-annealed (crystalline) films. Structural and morphological properties of the Film/SiO2/Si interfaces were also examined.
Study of metal gate work function modulation using plasma and SiH4 treated TiN thin films
Authors: Fillot F. , Maîtrejean S. , Farjot T. , Guillaumot B. , Chenevier B. , Passemard G. 
Published: April 2011

ABSTRACTAs gate oxide thickness decreases, the capacitance associated with the depleted layer in polysilicon gate becomes significant, making it necessary to consider alternative gate electrodes. Titanium nitride (TiN) films elaborated with TiCl4 precursor is widely studied as metal gate in semi-conductor technology. In this work, a study of TiN metal gate deposited by MOCVD using TDMAT (Tetrakisdimethylamino titanium) precursor is proposed. N2, H2 plasma application and SiH4 treatment after TiN thin film growth modify composition and microstructure. Consequently, they alter the physical properties of films. Such treatments may be a way to modulate work function and thus to control threshold voltage.Metallic layers were deposited in a chamber using a commercial 8 inch wafer deposition tool. In this study, structural and compositional properties of TiN were correlated with work function measurements. Firstly, the composition evolution (carbon content) was studied by AES and SIMS as a function of plasma and SiH4 treatments; XRD gave details on the microstructure. Secondly, MOS structures were processed on uniformly p-type doped wafers. C-V curves of capacitors were used to estimate the flat band voltage (VFB) and gave access to the work function, the effect of oxide fixed charges and the density of interface states. It is shown that as-deposited amorphous films exhibit a work function of 4.4 eV. Exposure to SiH4 is shown to increase this work function of about 150 meV. Thin films properties are not impacted by anneal treatments. Work function stability was tested at 425 °C, 900 °C and 1050 °C. Thermodynamic compatibility with gate oxide was verified thanks to experimental results and calculations.
Structural Comparisons of SiOx and Si/SiOx Formed by Passivation of Single-Crystal Silicon by Atomic and Molecular Oxygen
Authors: Kisa Maja , Twesten Ray D. , Yang Judith C. 
Published: April 2011

ABSTRACTThe structural characteristics of a silica layer and Si/SiO2 interface formed on Si single-crystal by oxidation in hyperthermal atomic oxygen (AO) and molecular oxygen (MO) at 493K were compared by wide variety of experimental techniques. The hyperthermal AO with kinetic energy of 5.1eV was created by the pulsed laser detonation of oxygen gas. The oxide formed by AO and MO on Si single crystal is amorphous as observed by HRTEM and selected area electron diffraction (SAED). However, the oxide formed by AO has a less random distribution of silicon and oxygen atoms as compared to the oxide formed by MO, as evidenced by the SAED patterns and EELS spectra. In contrast to MO formed silica, initial EELS results across the Si/SiO2 interface revealed no region of suboxides exists near the interface in the AO formed silica. The Si/SiO2 interface formed by AO species was found to be very abrupt and the oxide homogeneous, as opposed to the broad interface and non-homogeneous oxide created by MO, as determined by HRTEM and EELS.