bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of a New SrBi2Ta2O9 (SBT) Chemical Solution Using Crown Ether and its Thin Film Deposition
Authors: Min Yo-Sep , Lee June Key , Lee In-Sook 
Published: April 2011

AbstractA new chemical solution for the deposition of SrBi2Ta2O9 (SBT) thin films using crown ether is proposed. Crown ether enhances the solubility of bismuth acetate in acetic acid, which makes a solvent solution possible. A metal acetate-based SBT precursor solution was prepared in acetic acid using 18-crown-6, strontium acetate, bismuth acetate and tantalum ethoxide. (115)-preferentially oriented ferroelectric SBT thin films were formed on Pt/TiO2/SiO2/Si substrates by spin-coating with the new solution. After post-annealing at 800°C, a hysteresis loop obtained from a 2000Å thick SBT film with Pt electrodes showed a remanent polarization of ∼3μC/cm2 and a coercive voltage of ∼50kV/cm. It was shown from SIMS depth profiles that excess bismuth atoms in the SBT thin film diffused towards the Pt electrodes during post-annealing.
A Study on the Selective Nucleations for Formation of Large Single Grains in PZT Thin Films
Authors: Lee Jang-Sik , Park Eung-Chul , Park Jung-Ho , Lee Byung-Il , Joo Seung-Ki 
Published: April 2011

AbstractSelective nucleation and lateral growing method have been developed for high quality ferroelectric PZT(65/35) thin films using perovskite-phase PZT island seed. The PZT films on PZT seed island were transformed into the perovskite phase at temperatures as low as 540°C, which is 150°C lower than compared to that of PZT thin films deposited on Pt films. The temperature difference enables lateral growth without undesirable random nucleation. Maximum grain sizes of the perovskite-phase PZT films were determined by the annealing temperature. The PZT thin films show a leakage current density of 8×10−8 A/cm2, breakdown field of 1240 kV/cm, saturation polarization of 42 μC/cm2, and remanent polarization of 30 μC/cm2, whose values were maintained up to 2×1011 cycles. In this study, we show that when there was no grain boundary in the area measured, degradation such as fatigue and retention was not observed even with Pt electrodes. So the main source of degradation is the grain boundary in the PZT thin films.
Thickness Dependence and Electrical Properties of Ultrathin PZT Films Grown on SrRuO3/SrTiO3 by MOCVD
Authors: Shimizu M. , Fujisawa H. , Niu H. 
Published: April 2011

AbstractEpitaxial Pb(Zr,Ti)O3 (PZT) thin films with various thicknesses ranging from 40 to 400nm were prepared on SrRuO3/SrTiO3 by metalorganic chemical vapor deposition (MOCVD). The dependence of lattice constant on the film thickness and temperature was examined. The PZT films obtained showed ferroelectric hysteresis loops even when film thickness was 40nm. Applied voltage for obtaining high polarization density decreased as film thickness decreased. The 40nm-thick PZT film had the polarization density (Pr) of 38mC/cm2 at an applied voltage (Vc) of 0.7V.
Observations of Domain Structure at Initial Growth Stage of PbTiO3 Thin Films Grown by Mocvd
Authors: Fujisawa H. , Shimizu M. , Niu H. , Honda K. , Ohtani S 
Published: April 2011

AbstractDomain structure and growth mechanism of PbTiO3 thin films were investigated using a transmission electron microscopy(TEM) from the viewpoint of size effects. At initial growth stage of (111)-oriented PbTiO3 films prepared by metalorganic chemical vapor deposition(MOCVD), triangle-shaped islands were grown on Pt(111)/SiO2/Si before becoming a continuous film. Triangular islands grew gradually in a lateral dimension. This means that PbTiO3 films grew two-dimensionally at initial growth stage. In cross-sectional TEM photomicrographs, (101)-twin boundaries (90° domain walls) and inclination of {110} or {101}-plane were observed in PbTiO3 islands. This result indicates that such small PbTiO3 islands have a tetragonal structure and could have spontaneous polarization. The minimum island which had 90° domain walls was 10nm high and 18nm wide.
Near-Field Second Harmonic Microscopy of Thin Ferroelectric Films
Authors: Smolyaninov I. I. , Liang H. Y. , Lee C. H. , Davis C. C. , Rotter L. D. , Kaiser D. L. 
Published: April 2011

AbstractNear-field second harmonic microscopy is ideally suited for studies of local nonlinearity and poling of ferroelectric materials at the microscopic level. Its main advantages in comparison with other scanning probe techniques are the possibility of fast time-resolved measurements, and substantially smaller perturbation of the sample under investigation caused by the optical probe. We report second harmonic imaging of the surface of thin BaTiO3 films obtained in a near-field microscopy setup using a Ti:sapphire laser system consisting of an oscillator and a regenerative amplifier operating at 810 nm. Optical resolution on the order of 80 nm has been achieved.
Effect of TiN Treated by Rapid Thermal Annealing on Properties of BST Capacitors Prepared by RF Magnetron Co-sputter System at Low Substrate Temperature
Authors: Teng T. H. , Hwang C. C. , Lai M. J. , Huang S. C. , Chen J. S. , Jaing C. C. , Cheng H. C. 
Published: April 2011

AbstractIn this work, (Ba0.7Sr0.3)TiO3 thin films on Pt/TiN/Ti/Si substrate were deposited by an
RF magnetron co-sputter system at 300°C in an Ar+O2 mixed ambient. In the integration of BST capacitors, the diffusion barrier (TiN) under bottom electrodes is one of the key issues. To obtain a stable and excellent diffusion barrier against inter-diffusion between Pt and Si, as well
as against being oxidized during BST deposition, TiN was treated by a rapid thermal annealing (RTA) process. Experimental results indicated that proper RTA treatments resulted in a superior TiN barrier layer. In addition, low substrate temperature during BST deposition suppressed the phenomena of inter-diffusion and barrier oxidation. Furthermore, Pt hillocking, another problem during BST deposition because of high thermal budget, was also solved by
reducing substrate temperature during BST deposition. The MIM (Pt/BST/Pt) structure was used in the experiments for electrical properties measurement. High dielectric constant (εr =300), low leakage current (l.5×10−8 A/cm2) under 0.1MV/cm, and 10 year lifetime under 1.6MV/cm were achieved with an Ar+O2 mixed ambient at a low substrate temperature (300°C).
Densification and Evolution of Stress Development in Solution Derived PbZr0.53Ti0.47O3 Thin Layers
Authors: Park Sang M. 
Published: April 2011

AbstractStress development in thin layers of PbZr0.53Ti0.47O3 (PZT) and PbTiO3 (PT) prepared by sol-gel processing was monitored by in situ laser reflectance measurements. Layers were spin coated onto silicon substrates and thermally cycled to 600°C and 650°C. The shrinkage normal to the film plane was determined by in situ ellipsometry and scanning electron microscopy. Both PZT and PT multilayers showed a similar stress behavior on heating, but quite different behavior on cooling. As the film became dense at high temperatures, total stress was dominated by the thermal expansion mismatch between the oxide layer and the substrate. On cooling, the PT multilayers, which already crystallized into the perovskite structure, ended nearly stress free at room temperature, whereas mostly amorphous PZT multilayers were under a high tensile stress. Densification in PZT layers appeared to occur between 370°C and 520°C. At near 370°C the shrinkage mode for a single PZT layer was also observed to change substantially. A two-stage sintering process employing 450°C-sintering and 650°C-crystallization was found to be as effective as direct furnace insertion method in producing a dense film.
Oxygen Deficiency and Vacancy Formation in LSCO/PLZT/LSCO Capacitors
Authors: Friessnegg T. , Nielsen B. , Ghosha V. J. , Aggarwal S. , Keeble D. J. , Poindexter E. H. , Ramesh R. 
Published: April 2011

AbstractVacancy type defects in La0.5 Sr0.5CoO3/Pb0.9La0.1Zr0.2 Ti0.8/La0.5Sr0.5CoO3 capacitors were investigated by positron depth profiling. Post-growth annealing of the capacitor structure in oxygen deficient atmosphere exhibits the formation of vacancy type defects in all layers. A significant increase in open volume defects was found in the top and bottom electrode. The changes in the bottom electrode were studied more closely by etching off the top layer.
Integrated Thin Film Capacitor Arrays Utilizing Sol-Gel Derived Ferroelectrics
Authors: Liu David , Makl Steve , Heistand Robert H. 
Published: April 2011

AbstractNiobium-doped lead zircomate titanate (PNZT) thin film dielectric material has been produced on a large scale using a thick-coating sol-gel process. The material has been applied to the fabrication of commercial integrated capacitor array devices. Compared to conventional processes, this low-cost, long-shelf-life procedure had at least a 4-fold processing time enhancement. The specific capacitance of 2500 nF/cm2 and integrated density of over 200 component/cm2 have been demonstrated. The frequency domain capacitance measurement of integrated PNZT capacitors exhibits a frequency-independent behavior up to 2 GHz when a DC bias is applied. Leakage-voltage dependence follows the space-charge-limited-current (SCLC) mechanism. The fabricated integrated capacitor arrays pass the industrial standard of reliability for discrete multilayer capacitors.
Coplanar Capacitors with High Dielectric Constant BaSrTiO3 for Microwave Application
Authors: Hu Wei , Fuflyigin Vladimir , Chi Jim 
Published: April 2011

AbstractA coplanar structure is shown to be free of the asymmetrical I-V characteristics normally observed in MIM capacitors with BST inter-electrode dielectric. The low barrier height at the bottom interface is found to be responsible for the asymmetry, which causes increased leakage current and reduced breakdown voltage in one bias polarity. These problems can be eliminated using a coplanar structure, which has been shown elsewhere to have a very low parasitic inductance and a very high resonant frequency. However, these improvements are realized at the cost of a four times reduction of capacitance per unit area.
Ferroelectric Properties of II-VI Type Semiconducting Thin Films on Si(100)
Authors: Hotta Y. , Tabata H. , Kawai T. 
Published: April 2011

AbstractWe have demonstrated the presence of ferroelectric properties in non-oxide (II-VI type semiconductor) ferroelectric thin films, such as (Zn,Cd)Te, (Zn,Cd)Se and (Zn,Cd)S (thickness: 3000–5000 Å). They have shown the ferroelectric hysteresis feature with memory windows of 0.2V, 0.3V and 0.8V, respectively. The materials design for getting the ferroelectric nature is as follows: when the size of the replaced atom is smaller than the host atom, then the substituent atoms can occupy off-centered positions, thus locally induce electric dipoles, thereby leading to ferroelectric behavior. These II-VI wide gap semiconducting ferroelectric films will open the door for new memory devices.
Dielectric and Transverse Piezoelectric Characterization of Sol-Gel Derived Pb(Mg1/3Nb2/3)O3-PbTiO3 (70/30) FILMS WITH {100} and {111} Textures
Authors: Park Jeong Hwan , Trolier-McKinstry Susan 
Published: April 2011

AbstractHighly {100} and {111} oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 (70/30) films were deposited on Pt(111)-passivated silicon substrates using a modified sol-gel process. In both cases, the degree of preferred orientation did not change with film thickness from 0.56 μm to 1.5 μm. The room temperature dielectric constants for the {100}-oriented films were 2100–2650, while those for the {111} oriented films were 1900–2350. In both cases tan δ was less than 0.03. It was found that the piezoelectric coefficient (d31) of the PMN-PT films increased with increasing film thickness. The d31 coefficient of highly {100} oriented PMN-PT films poled for 5 minutes at 85 kV/cm were found to range from –45 to –86 pC/N assuming a Young's modulus of 35 GPa. Highly {100} oriented PMN-PT films showed larger piezoelectric coefficients than {111} oriented films. Results on aging of the piezoelectric coefficients for the differently oriented films are also presented.
Preparation of Piezoelectric PZT Thin Films by Mocvd for MEMS Applications
Authors: Chen Ing-Shin , Kim Dong-Joo , Maria Jon-Paul , Roeder Jeffery F. , Kingon Angus I. 
Published: April 2011

AbstractIntegration of piezoelectric Pb(Zr,Ti)O3 (PZT) thin films promises to provide silicon-based microelectromechanical systems (MEMS) with added functionality. PZT films with compositions near the tetragonal/rhombohedral morphotropic boundary have been deposited on iridium-coated Si substrates by a thermal chemical vapor deposition (CVD) process using flash vaporized metalorganic precursors. Process variables including (A-site)-to-(B-site) ratios in the precursor mix and deposition times have been surveyed. Stoichiometric, perovskite films with nominal Zr/Ti ratios ranging from 40/60 to 60/40 were obtained. Parallel-plate capacitor structures have been fabricated by depositing Pt top electrodes using e-beam evaporation through shadow masks. Ferroelectric hysteresis loops were measured using a standard ferroelectric tester. Remenant polarization values in the range of 20∼30 μC/cm2 were obtained. For films of 0.5 μm or thicker, piezoelectric hysteresis loops were characterized by dual-beam interferometry. Longitudinal piezoelectric coefficients (d33) of 30∼60 pm/V were observed on the films deposited between 550 and 600°C.
(001)-Oriented LaNiO3 Bottom Electrodes and (001)-Textured Ferroelectric Thin Films on LaNiO3
Authors: Zhang Zhenshan , Park Jeong Hwan , Trolier-McKinstry Susan 
Published: April 2011

AbstractIn this work, highly (001)pc-oriented thin films of LaNiO3 (LNO) were deposited by DC magnetron sputtering onto Si substrates (pc = pseudocubic indices). The target powder was prepared using a molten salt technique with Na2CO3 as a flux. The final target density was greater than 85% of theoretical density. The best results were obtained when sputtering was carried out at a power of 186 W and a working pressure of 45 mtorr with a gas composition of 50% O2 + 50% Ar. The thickness of the deposited films was proportional to the sputtering time, and the growth rate was 300Å/hour. Highly (001)-oriented thin films of lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (PZT) and Pb[(Mg1/3Nb2/3)0.7Ti0.3]O3 (PMN-PT) were fabricated by a sol-gel method on (001)-textured LNO metallic oxide electrodes. A remanent polarization of 12 μC/cm2 and d31 of -125 pC/N (assuming a Young's modulus of 35 GPa) were measured on the PMN-PT thin films with a thickness of 0.9 μm. This piezoelectric coefficient considerably exceeds that available from PZT films, and depends critically on the film orientation. Changes in the hysteresis loop due to externally applied stress will also be described.
High Density Dry Etching of (Ba,Sr)TiO3 and LaNiO3
Authors: Lee K. P. , Jung K. B. , Srivastava A , Kumar D. , Singh R. K. , Pearton S. J. 
Published: April 2011

AbstractHigh density plasma etching of (Ba,Sr)TiO3 (BST) and LaNiO3 (LNO) thin films was performed in two different plasma chemistries, Cl2/Ar and CH4/H2/Ar. While the latter chemistry produced extremely low etch rates (≤ 100 Å-min−1) under all conditions, the Cl2/Ar produced a smooth anisotropic pattern transfer. The etching was still strongly ion-assisted, but maximum removal rates of ∼900 Å min−1 for both materials were achieved with selectivities of ∼16 for BST and ∼7 for LNO over Si. A single layer of thick (∼7 μm) photoresist is an effective mask under these conditions.
Narrow Resonance Profiling Study of the Oxidation of Ti1-xALxN Barrier Layer
Authors: Hugon M. C. , Desvignes J. M. , Letendu F. , Agius B. , Vickridge I , Kim D. J. , Ayguavives F. , Kingon A. I. 
Published: April 2011

AbstractThe preparation of ferroelectric and high dielectric perovskite materials, which is performed at high temperature (550–750°C) in oxidizing environments, provides strong limitations on the choice of electrode materials which have to be used for integration with semiconductor devices. To minimize interdiffusion and oxidation reactions, a diffusion barrier must be placed between Si substrate and electrode material (Pt, lrO2, RuO2.…). Ti1-xAlxN thin films, deposited by reactive sputtering, are promising materials as electrically conductive layers and robust diffusion barriers. The stability of these films has been investigated at conditions typically used for crystallization of perovskite dielectrics. Films with various Al composition (x=0, 0.1, 0.2 and 0.4) have therefore been annealed by RTA (rapid thermal annealing) in 18O2 at 550–750°C. The concentration depth profiles of both 18O and 27A1 were measured before and after the RTA treatments via the narrow resonances of 18O(p,α)15N at 151 keV (fwhm=100 eV) and 27Al(p,γ)28Si at 992 keV (fwhm=100 eV). Al incorporation in the films reduces oxide growth especially at high annealing temperatures. The Al excitation curves indicate a uniform Al content for as deposited Ti1−xAlxN, and reveal Al diffusion to the surface during oxidation which indicates the formation of an Al rich oxide layer at the Ti1-xAlxN surface.
From Ferroelectrics to Polymers - Perspectives for Thin Film Optical Waveguides and Devices
Authors: Buchal Christoph 
Published: April 2011

AbstractPresently commercial optical fiber links experience an explosive growth. On the other hand, the integration of optical functions on a single substrate (“Integrated Optical Device”) is still mostly limited to the R & D-laboratories. Only Mach-Zehnder modulators, made from ferroelectric crystals, have found commercial applications so far. The development phase of the integrated optical devices, based on bulk crystalline LiNbO3, is now covering a time span of nearly 30 years. In comparison, the development of the thin film growth of optical oxide ferroelectrics or of tailored optical polymers is just a few years old and we are still at the beginning of the learning curve.
Luminescence Efficiency of Erbium-Doped BaTiO3 Thin Films
Authors: Teren A. R. , Wessels B. W. 
Published: April 2011

AbstractThe factors limiting the efficiency of Er3+ luminescence at 1.54 μm (0.8 eV) in erbiumdoped barium titanate films were studied. To investigate the effect of film stoichiometry on luminescence efficiency films were annealed in oxygen and in vacuum. For films annealed in oxygen at temperatures of 700–900°C a nominal increase in the luminescence efficiency was observed. Vacuum annealing resulted in strong quenching of the emission intensity. Transient photoluminesence measurements showed that the emission lifetime also decreased for the reduced films. This effect was reversible; upon oxygen annealing both the emission intensity and lifetime were restored to their original values. These results indicate that the Er3+ luminescence efficiency strongly depends on film stoichiometry.
Photorefractive Conjugated Polymer-Liquid Crystal Composites
Authors: Wasielewski M. R. , Yoon B. A. , Fuller M. , Wiederrecht G. P. , Niemczyk M. P. , Svec W. A. 
Published: April 2011

AbstractA new mechanism for space-charge field formation in photorefractive liquid crystal composites containing poly(2,5-bis(2′-ethylhexyloxy)-l,4-phenylenevinylene) (BEH-PPV) and the electron acceptor N,N′-dioctyl-1,4:5,8-naphthalenediimide, NI, is observed. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 μm. We show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile species due to hole migration along the BEH-PPV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.
Investigation of Optical Limiting Mechanism in Multiwalled Carbon Nanotubes
Authors: Sun X. , Xiong Y. N. , Chen P. , Lin J. Y. , Ji W. , Lim J. H. , Yang S. , Hagan D. J. , Stryland E. W. Van 
Published: April 2011

AbstractWe report an investigation into the mechanism responsible for the optical limiting behavior in multiwalled carbon nanotubes. We conducted energy-dependent transmission measurements, picosecond time-resolved pump-probe, and nonlinear scattering experiments at 532-nm wavelength on multiwalled carbon nanotube suspension. For comparison, C60-toluene solution and carbon black suspension were also studied in the same experiments. The similarities that we observed between the multiwalled carbon nanotubes and carbon black suspension suggest that nonlinear scattering, which is known to be responsible for the limiting action in carbon black suspension, should play an important role in the limiting effect in multiwalled carbon nanotubes.
Control of Location and Carrier-Interaction of Erbium Using Erbium-Doped Si/SiO2 Superlattice
Authors: Han Hak-Seung , Lee Won-Hee , Shin Jung H. 
Published: April 2011

AbstractThe effect of controlling the interaction between the erbium atoms and the carriers of the host matrix is investigated using erbium doped Si/SiO2 superlattices. Based on the previous finding that controlling the location of the erbium atoms by doping only the SiO2 layers improves both the Er3+ photoluminescence intensities and the temperature quenching of the Er3+ luminescence, we identify controlling the interaction between erbium atoms and the carriers in the Si layer to be the key point. We demonstrate that by further isolating the erbium atoms from the Si layers by depositing thin buffer layers of pure SiO2 improves the Er3+ photoluminescence by several orders of magnitude while still allowing efficient excitation by carriers to dominate. Finally, we demonstrate that efficient waveguides can be fabricated using such erbium doped Si/SiO2 superlattices.
Experimental Study and Modeling of Nonlinear Scattering in Polymer Dispersed Liquid Crystals
Authors: Pacilli M. , Sebbah P. , Sixou P. , Vanneste C. , Guillard H. 
Published: April 2011

AbstractWe investigate the optical limiting capabilities of composite materials consisting of nematic liquid crystal inclusions within a polymer matrix in the millisecond and CW regime. Preparation of the composite has been optimized to decrease the operation voltage. Clear evidence of light induced reorientation is observed. A numerical model is proposed to describe multiple linear and nonlinear light scattering in the time domain in this medium. Numerical simulations are compared to experiment and confirm promising limiting characteristics of such materials.