bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Ferroelectric Properties of Vinylidene Fluoride Oligomer Evaporated Films
Authors: Noda K. , Ishida K. , Mochizuki K. , Kubono A. , Horiuchi T. , Yamada H. , Matsushige K. 
Published: April 2011

ABSTRACTStructures and electrical properties of newly synthesized vinylidene fluoride (VDF) oligomer [CF3(CH2CF2)17I] films evaporated onto various substrates around liquid nitrogen temperature were investigated. As a result, the VDF oligomer films were mainly formed with ferroelectric phase (form I) crystals and the molecular chains were oriented parallel to the substrate surfaces regardless of both the kind of the substrates and the thickness of the VDF oligomer films. In addition to these properties, the VDF oligomer films showed polarization reversal due to 180° rotation of the polar VDF oligomer molecules according to the applied voltages. This ferroelectric behavior was verified by local poling and piezoresponse measurements with an atomic force microscope, and by measurements of D-E hysteresis curves.
Structural and Vibrational Properties of Ferroelectric Pb1-xSrxTiO3 Thin Films and Powders
Authors: Jain M. , Savvinov A. , Dobal P. S. , Majumder S. B. , Katiyar R. S. , Bhalla A. S. 
Published: April 2011

ABSTRACTIn this work we present the structural, and vibrational properties of ferroelectric Pb1-xSrxTiO3 (PST). Thin films of PST were prepared by using sol-gel technique for various compositions with x values ranging from 0.0–1.0. Respective compositions were also prepared in ceramic and powder forms using sol-gel and solid-state reaction methods. X-ray diffraction was used for the structural characterization of these materials. Raman spectroscopy was utilized to study the phases and lattice vibrational modes, especially the soft mode in PST compositions. The temperature dependence of the soft mode frequency for different PST compositions revealed that the phase transition temperatures increased with increasing Pb contents in PST system. Ferroelectric properties of the films were correlated with the substitution-induced changes in the material.
Submicron Ferroelectric Elements Fabricated by Direct Electron Beam Lithography
Authors: Kim Dong-Joo , Im Jin Seo , Thompson Carol , Streiffer S. K. , Wiederrecht G. , Auciello O. 
Published: April 2011

ABSTRACTTo realize Gigabit density ferroelectric memory devices, downscaling issues involving processing, materials, and fundamental ferroelectric behavior must be resolved. To address patterning and characterizing ferroelectric films at the nanoscale, we have prepared different lateral sizes of ferroelectric PZT capacitors down to 120 nm, using direct-write electron beam lithography. Characterization of the piezoelectric activity of the patterned elements was performed by means of piezoelectric-sensitive scanning probe microscope in the contact mode. Switching of single 120 nm cells was achieved.
Dielectric Properties of (Ba,Sr)TiO3 Thin Film Capacitors Fabricated on Alumina Substrates
Authors: Koutsaroff I. P. , Kassam A. , Zelner M. , Woo P. , McNeil L. , Bernacki T. , Cervin-Lawry A. , Patel A. 
Published: April 2011

ABSTRACTDouble layer (DL) Ba0.7Sr0.3TiO3 (BST) capacitors with Pt electrodes have been fabricated with similar growth conditions on different substrates. The substrates used in the present study were r-plane sapphire, polycrystalline alumina Al2O3 (99.6% and 96%), and glazed polycrystalline alumina. BST films were grown by metal-organic decomposition (MOD) method. By varying the annealing conditions which affects the formation of the crystalline structure, significant changes in the dielectric properties of the BST films have been observed. BST films were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Powder X-ray Diffractometer (PXRD). These observations showed that BST films grown at lower temperatures on alumina substrates exhibited the smallest grain size. BST films of the same thickness prepared under the same thermal processing conditions showed higher capacitance when grown on all types of alumina-based substrates compared to those deposited on control SiO2/Si. The higher capacitance on alumina was always associated with larger dissipation factor, and lower or similar leakage current density. The final tuning, of the dielectric properties of BST DL capacitors on non-silicon substrates, was correlated to the initial film formation temperature and post-annealing conditions of the BST films. The leakage current density, of DL BST capacitors fabricated on glazed alumina, becomes smallest when the BST processing temperature was lowered by 100 °C compared to the control SiO2/Si. The typical achieved leakage current density for 1500×1500 μm2 DL capacitors on glazed alumina was 3.8×10-9 A/cm2 at 250 kV/cm (36.5 fF/μm2), about 3 times lower than on SiO2/Si substrates (1.1×10-8 A/cm2 at 250 kV/cm, 31 fF/μm2).
Leakage Current Experiments in STO and BST Thin Films
Authors: Schroeder Herbert , Schmitz Sam 
Published: April 2011

ABSTRACTWe have performed experiments on steady state leakage currents through insulating thin films of high permittivity dielectrics such as strontium-titanate (STO) and barium-strontium-titanate (BST) in order to contribute to the understanding of the mechanism limiting the current. Furthermore, as BST is a candidate as a dielectric in the capacitor of future Gb-generation DRAM cells, the absolute value of the current in dependence of external parameters is interesting for the application.Besides external parameters such as applied voltage and temperature we have investigated the dependence on dielectric film thickness between 20 nm and 150 nm with symmetrical Pt electrodes. For some selected films the influence of asymmetric electrodes has also been investigated: While the bottom electrode was always Pt, the top electrodes were Pt, Au and Al. An epitaxial STO film with oxide electrode bottom electrode has also been tested.The main results are as follows:The field dependence of the leakage current quite often shows a linear behavior in a “Schot-tky”-plot, i.e. log (current density) vs. sqrt (applied field). At constant applied field the thinner films show much lower leakage currents than the thicker ones. The leakage currents increase using Pt, Au and Al as cathode, respectively. The leakage in the epitaxial STO film is much smaller with an oxide electrode (SrRuO3) as cathode than with a platinum one.All these results will be discussed within a modified model, in which the current is bulk-limited, and compared to numerical simulation results of this model.
Influence of Ta2O5, TiO2, and ZrO2 Interfacial Layers on Structural and Electrical Properties of Laser Ablated Ba0.5Sr0.5TiO3 Thin Films
Authors: Das Suprem R. , Das Rasmi R. , Bhattacharya P. , Katiyar Ram S. 
Published: April 2011

ABSTRACTPulsed laser deposition technique was used to fabricate Ba0.5Sr0.5TiO 3 (BST) thin-films on Pt/TiO 2/SiO2/Si substrates. The influence of thin interfacial layers of Ta2O5, TiO2, and ZrO2, on the structural and electrical properties of BST thin films was investigated. Insertion of interfacial layers does not affect the perovskite phase formation of BST thin films. Buffer layers helped to make uniform distribution of grains and resulted in a relative increase in the average grain size. The dielectric tunability of BST thin films was reduced with the presence of buffer layers. A BST thin film having a dielectric permitivity of 470 reduced to 337, 235 and 233 in the presence of Ta2O5, TiO2, and ZrO2 layers, respectively. The reduction of the relative dielectric permittivity of BST films with the insertion of interfacial layers was explained in terms of a series capacitance effect, due to the low dielectric constant of interfacial layers. The TiO2 layer did not show any appreciable change in the leakage current density. Deposition of thin Ta2O5 and ZrO2 interfacial layer on top of Pt reduced the leakage current density by an order of magnitude.
Thin Film Capacitors Cut from Single Crystals Using Focused Ion Beam Milling
Authors: Saad M. M. , Donnelly N. J. , Bowman R. M. , Gregg J. M. 
Published: April 2011

ABSTRACTThe Focused Ion Beam Microscope (FIB) has been used to fabricate capacitors from single crystals of BaTiO3 and SrTiO3 with electrode areas ∼200μm2, and thickness of single crystal dielectric between 2μm and 500nm. Cross-sectional transmission electron microscopy revealed that during capacitor fabrication, the FIB rendered around 20nm of dielectric at the electrode-dielectric interface amorphous, associated with local gallium impregnation. Such a region would act electrically in series with the single crystal and would presumably have a considerable negative influence on dielectric properties. However, annealing prior to electrode deposition was found to fully recover the single crystal, and homogenise the gallium profile. Some subsequent dielectric testing of SrTiO3 was performed yielding a room temperature dielectric constant of ∼150 and loss tangent of 0.015 at 100kHz. A technique has therefore been demonstrated which allows fabrication of capacitors in which size-effects in ‘thin-films’ can be studied, without the influence of grain boundaries, and other issues associated with conventional thin film growth.
Characterization of Shape Memory and Superelastic Effects by Instrumented Indentation Experiments
Authors: Ni Wangyang , Cheng Yang-Tse , Grummon David S. 
Published: April 2011

ABSTRACTThe shape memory and superelastic effects of martensitic and austenitic NiTi alloys were studied by instrumented indentation experiments. The shape memory effect was quantitatively characterized by the thermo-activated depth recovery ratio of the residual indentation depth. The superelasticity of austenitic NiTi was quantitatively characterized by the depth and work recovery ratios obtained from the load-displacement curves. The shape memory and superelastic effects under different indenters (Berkovich, Vickers, and spherical) and loads were rationalized using the concept of the representative strain and maximum strain. This study demonstrates that instrumented indentation techniques are useful in the quantitative characterization of the shape memory and superelastic effects in micro- and nano-meter length scale.
Film Stress Characterization Using Substrate Shape Data and Numerical Techniques
Authors: Feng Zhaohua , Lovell Edward G. , Engelstad Roxann L. , Mikkelson Andrew R. , Reu Phillip L. , Sohn Jaewoong 
Published: April 2011

ABSTRACTIntrinsic stress in a film-substrate system can have deleterious effects. To facilitate an understanding of stress generation and control film quality, measuring film stress is essential. In recent years research laboratories and industry have increasingly adopted indirect methods, which are usually based on the measurement of substrate deformation. The film stress is calculated by equations relating the stress to the deformation, such as the well-known Stoney's equation. However, when the two principal stresses at each point in the film plane are not equal and their distribution is nonuniform, the local application of Stoney's equation does not provide correct stress results. A numerical technique is presented, which overcomes these limitations and makes accurate stress determination possible.
Interaction of C60 with Isoelectronic Surfaces: Graphite and Hexagonal Boron Nitride
Authors: Reinke P. , Feldermann H. , Oelhafen P. 
Published: April 2011

ABSTRACTIn the present study we focus on the interaction of C60 with sp2 boron nitride (BN), a surface that is isoelectronic to graphite. The nanocrystalline BN substrate was deposited by mass selected ion beam and consists of an sp2 surface layer, which covers a cubic-BN film. The interaction and electronic properties of the C60-BN system are observed by photoelectron spectroscopy in the x-ray (XPS) and ultraviolet regime (UPS). The experiment is initiated by sequential deposition of C60 and the overlayer growth proceeds via island formation. In a second step the sample is annealed at a rate of 5–10 K/minute while simultaneously recording the UPS spectra. The majority of C60 desorbs from the sp2 BN surface at 493 K. The remaining C60 (initially about 0.6 ML) is gradually removed with increasing temperature (up to 813 K) but never completely desorbed and presumably attached at surface imperfections or grain boundaries of the nanocrystalline material. No carbide formation, preferential interaction of C60 with either element or a charge transfer are observed. The presence of C60 induces an upward band bending and related peak shifts in the sp2 BN surface layer and to a lesser extent in the underlying c-BN bulk. An upward band bending is likewise observed in the C60 overlayer, and the Fermi level has therefore to be pinned by defects in the interface region. The layered structure of the BN film allows to probe the extension of the space charge layer in the BN film.
Microstructure and Stress Analyses of Copper Films Deposited on Biased Substrates by Microwave Plasma-Assisted Sputtering
Authors: Thièry François , Pauleau Yves , Arnal Yves , Pelletier Jacques , Ortega Luc 
Published: April 2011

ABSTRACTPure copper films have been deposited on <100> Si substrates either at the floating potential or biased to various dc voltages ranging from 0 to - 125 V. Argon ions from the discharge produced in a distributed electron cyclotron resonance microwave plasma reactor were used for sputtering of a copper target biased to various dc voltages. For sputter deposition, the Si substrates placed on a water-cooled substrate holder were maintained at ambient temperature. The argon pressure was 0.13 Pa and the dc target voltage was fixed at - 600 V. The deposition rate of films was investigated as a function of the substrate bias voltage. The crystallographic structure of films and size of copper crystallites were determined by x-ray diffraction analyses. The surface morphology of films was examined by atomic force microscopy. The electrical resistivity of films was deduced from the thickness and sheet resistance of films determined by profilometry and four point probe measurements, respectively. The magnitude of residual stresses in copper films was calculated from the radius of curvature of Cu/Si samples deduced from profilometry measurements. The evolution of the microstructure, surface morphology and electrical resistivity of films as well as the magnitude of residual stresses developed in these films were studied as functions of the substrate bias voltage. These major characteristics of films were found to be dependent on the energy of argon ions impinging on the surface of films grown on biased substrates. The effect of the ion energy on the physical features of films is analyzed and discussed in this paper.
Surface Modification of Sputtered SiO2 Thin Films by Metal Doping
Authors: Takeda Satoshi , Fukawa Makoto 
Published: April 2011

ABSTRACTThe effects of metal doping on the surface properties of sputtered silicon dioxide (SiO2) thin films were investigated. The aluminum (Al), titanium (Ti) or zirconium (Zr) doped SiO2 thin films were deposited onto glass by RF magnetron sputtering. The optical transmission spectra of the films were almost same as that of undoping film when the doping concentration was lower than ∼3 at %. The contact angle of water droplets was measured for the films as a function of elapsed time. The hydrophobicity, resulting from the adsorption of organic substances in the atmosphere, was significantly altered by the metal doping. The surface reactivity of the film with a fluoroalkyl isocyanate silane was also changed. These alternations were due to the difference in surface OH group density of the film, which was induced by the metal doping. These results suggest that the surface properties can be modified by controlling the surface OH group density of the films.
Surface Modification and Characterization of Plasma Sprayed Alumina Coatings using Lasers
Authors: Krishnan R. , Dash S. , Kesavamoorthy R. , Babu Rao C. , Tyagi A. K. , Raj Baldev 
Published: April 2011

ABSTRACTA synergetic way of combining superior properties of ceramics with that of metals is to apply ceramic coatings over metallic substrates. Also, ceramic coatings provide better protection of the covered metal under concomitant corrosion and wear conditions. Of all the advanced ceramic materials, Al2O3 is widely used due to its low cost and availability in high purity forms. But the alumina coatings made through Air Plasma Spray suffers from major disadvantages such as presence of metastable γ-Al2O3 phase, high surface roughness and porosities. In this paper, we have shown the feasibility of transforming the γ-Al2O3 phase present in the as-sprayed coatings to a thermodynamically stable α-Al2O3 phase. A continuous wave CO2 laser having maximum power of 500W was used to provide a surface specific heating without affecting the metallic substrate. In addition to XRD, Raman scattering and photoluminescence investigations were carried out using a Ar+ laser to confirm the restoration of alpha phase and the reduction in porosity respectively. Also, 1 mW He-Ne laser operating in TEM00 mode was used to examine the reduction of surface roughness using laser scattering technique. The intensity of the specular reflection was used to quantify the surface roughness. Both reduction in surface roughness and porosity were evaluated using SEM micrographs taken on the surface and cross section of the coatings.
Attenuation of Surface Acoustic Waves by Carbon Nanotubes
Authors: Ciplys Daumantas , Rumyantsev Sergey , Shur Michael S. , Vajtai Robert , Wei Bingqing , Ajayan Pulickel , Gaska Remis , Rimeika Romualdas 
Published: April 2011

ABSTRACTA strong attenuation of surface acoustic waves in the range of 30 to 100 MHz by singlewalled carbon nanotube layers deposited on the surface of piezoelectric lithium niobate single crystal has been observed. The attenuation exhibits non-monotonous dependence on nanotube density. This attenuation is attributed to the acoustoelectronic interaction between electric fields of the SAW and charge carriers in the nanotubes. The experimental results are in the qualitative agreement with the theory of acoustoelectronic interaction in inhomogeneous structures.
Screen Printing of Carbon Nanotubes for Field Emission Displays
Authors: Yi Mann , Jung Hyuck , Seo Woo-Suk , Park Jong-Won , Chun Hyun-Tae , Koh Nam-Je , Han Soo-Deok , Lee Dong-Gu 
Published: April 2011

ABSTRACTCarbon nanotubes (CNTs) have been significantly used for the field emitters for display applications. It is necessary to investigate the process variables affecting the screen printing of carbon nanotubes for the fabrication of good-quality field emitter devices with uniformity. Screen printing techniques have some advantages such as the short processing time and lower processing cost. The carbon nanotube pastes for screen printing are normally composed of organic binders, carbon nanotubes, and some additive materials. In this study, the carbon nanotube emitters for field emission displays were fabricated with different processing variables such as paste viscosity, paste composition, screen mesh, etc. The CNT pastes were printed on Cr-coated/Ag-printed soda-lime glass substrates. As a result, the processing variables were optimized for the good screen printing. From the I-V characteristics, the turn-on field of single-walled nanotubes was lower than that of multi-walled nanotubes. The decrease in the mesh number of screen masks resulted in decreasing the turn-on field and increasing the electron emission current due to the higher density and vertical alignment of printed-CNTs.
The nucleation and growth of nano-structured diamond on phosphor and boron ions implanted Si substrates
Authors: Gu C. Z. , Wei L. , Sun Y. , Jia J. K. , Jin Z. S. 
Published: April 2011

ABSTRACTNanocrystalline diamond films deposited by microwave plasma chemical vapor deposition (MWPCVD) method were observed on Si substrates implanted with phosphor (P) and boron (B) ions at room temperature via scanning electron microscopy (SEM). The relations between the species, energies and doses of implanted impurities and the nucleation, grain size and morphology of diamond were studied. The results present that different nucleation density from 106 cm-2 to 109 cm-2 can be obtained on implanted and unscratched Si, which is larger of 3–6 magnitude orders than that on mirror-polished Si. The nano-structured diamond films can be deposited on scratched Si substrates implanted by higher concentration of phosphor and boron ions. The grain sizes of nano-structured films can be adjusted by controlling the implanted energies and doses, and nano-structured films can be synthesized with low impressive stress. The Raman spectroscopy was employed to analysis the phase purity of nano-structured film, which shows a broad peak at around 1150 cm-1 relative to the nano-structured and tetrahedrally bonded carbon network.
Modelling of the mechanical and tribological properties of coatings and surface treatments
Authors: Bull S. J. 
Published: April 2011

ABSTRACTOver the past few years a wide range of coatings and surface treatments have been developed to enhance component performance. Increasingly coating architectures are becoming more complex and multilayer, superlattice and graded coating systems are becoming widely available. This offers so many potential coating variants that it is almost impossible to envisage trying all the possibilities to optimise performance. The need for predictive performance models has never been more acute but model development has generally lagged behind the introduction of new coatings. For tribological coatings the mechanics of contact is particularly important if performance is to be understood. This paper briefly reviews developments in numerical simulation and extends recent modelling developments in an energy-based predictive model for the hardness and Young's Modulus of a coated system. The model predictions can be improved by considering the fracture behaviour of the coating.
A comparative microtribological investigation of diamond-like carbon films for applications in microsystems
Authors: Imad-Uddin Ahmed S. , Bregliozzi Giuseppe , Haefke Henry 
Published: April 2011

ABSTRACTThis study reports on the microfrictional properties under reciprocating sliding of different types of commercially available diamond-like carbon (DLC) films, prepared using low and high frequency plasma-assisted chemical vapor deposition (PACVD) and the vacuum arc method. Silicon and sapphire balls were used as counterbodies. Friction-load curves suggest that, for applied forces in the N to μN regime, two properties have a strong influence on the microfriction: First, the chemical composition plays a dominant role and second, the film roughness. With silicon against DLC, microfriction of hydrogen-free DLC films was greater than the hydrogen containing films. With sapphire counterbodies, microfriction was inversely proportional to film roughness. For all films tested, microfriction was independent of the sliding velocity. Mild wear in the form of scratches was observed only on silicon, while no wear could be detected on any of the DLC films. These results illustrate the utility of implementing microtribological testing in a coating development for microsystems.