bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure-hydrogen sorption property relationships in LaNi5-based alloys
Authors: Inui Haruyuki , Sakamoto Hiroki , Yamamoto Tokujiro , Yamaguchi Masaharu
Published: April 2011

The relationship between microstructures and hydrogen absorption-desorption properties described in terms of pressure-composition (P-C) isotherms has been investigated for binary and Co- and Al-added LaNi5-based alloys as a function of the number of hydrogen sorption cycles. From microstructure observations, factors determining absorption pressures are deduced and variations of P-C isotherms with cycle number for these three LaNi5-based alloys are discussed.
Water insertion in hydrophobic porous oxides
Authors: Carrière D. , Sidis S. , Lahlil K. , Moreau M. , Barboux P. , Boilot J.-P.
Published: April 2011

We have studied the synthesis of porous hydrophobic systems made from silica and zirconia. The silica systems have been grafted with alkyl-chlorosilanes. Alternative hydrophobic systems were also obtained by synthesis of colloidal monoclinic zirconia grafted with various alkyl phosphonates. The mechanism and the density of grafting were studied by solid state MAS NMR and nitrogen adsorption isotherms. The bulk thermodynamic properties of water are strongly dominated by the interfacial interactions at the surface of these porous solids. The penetration of water in these porous systems was studied by high pressure intrusion of water (water porosimetry between 0 and 100 MPa) into the hydrophobic pores. The amazing mechanical behavior of such water-porous body mixtures can find interesting applications for mechanical energy storage and dissipation.
Synthesis and Characterisation of B-Site Doped Cu2Ta4O12
Authors: Renner Bernd , Ebbinghaus Stefan , Reller Armin , Schrupp David , von Nidda Hans-Albrecht Krug , Heinrich Monika , Lunkenheimer Peter , Schetter Michael
Published: April 2011

We investigated synthesis, structure, composition as well as electric and magnetic properties of copper tantalum oxide single crystals and powder samples. It was possible to flux-grow single crystals of undoped Cu2Ta4O12. To modify the copper content in this structure, tetravalent and hexavalent ions like titanium and tungsten have been incorporated. Rietveld refinement data as well as magnetic and dielectric properties are presented.
A New Mechanism for the Catalytic Growth of Carbon Filaments and Metal Dusting Phenomenon
Authors: Zeng Zuotao , Natesan K.
Published: April 2011

Raman scattering and X-ray diffraction were used to study the mechanism of the catalytic crystallization of carbon and metal dusting. The following new mechanism is proposed for metal dusting and the growth of carbon filaments. Carbon cannot crystallize well by deposition from carburizing gases at low temperature without catalytic activation because of its strong C-C bonds and high melting temperature. The poorly crystalline carbon has higher free energy than that of good crystalline carbon. To form good crystalline carbon, carbon atoms have to dissolve, diffuse through metal particles, and crystallize on a proper lattice plane that can act as a template to help the epitaxial growth of carbon crystals. Metal particles are liberated from the pure metal and alloys in this process, which leads to metal dusting attack. The decrease of free energy from highly disordered to well crystalline carbon is the driving force for metal dusting and carbon filament growth through metal particles.
Effect of Precursor Salt on FeP Nanoparticle Formation
Authors: Perera Susanthri C. , Brock Stephanie L.
Published: April 2011

The formation of single phase FeP nanocrystals has been achieved by the reaction of Fe(III) salts (iron(III)acetylacetonate (Fe(acac)3) and iron(III)chloride (FeCl3)) with tris(trimethylsilyl)phosphine in trioctylphosphine oxide (TOPO)/trioctylphosphine (TOP) at elevated temperatures. The sizes of nanoparticles formed differ markedly depending on the initial iron salt used. Use of Fe(acac)3 always resulted in comparatively bigger particle formation (∼5 nm) while FeCl3 forms much smaller particles (∼1 nm) as confirmed by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM).
New Results for Electron Transport, Chemical Diffusion and Stability of Solid Oxygen Ion Conductors
Authors: Wiemhoefer H.-D. , Dogan M. , Luebke S. , Ruehrup V.
Published: April 2011

We describe the measurement of electronic conductivity of solid oxide electrolytes by a modified Hebb-Wagner technique based on the use of blocking microelectrodes. Results are presented for a couple of typical solid oxide electrolyte systems mainly derived from ceria and lanthanum gallate. The examples demonstrate a good resolution of the microelectrode technique in particular within the electrolyte domain, i.e. around the minimum of the electronic conductivity. This made possible the detection of deviations from the predicted oxygen partial pressure dependence of simple defect models for the concentrations of electrons and holes. The observed deviations from these defect models, at least partially, reflect the overemphasized ideality of the usually applied semiconductor model.

Whereas the effect of dissolved transition metals with variable valence states such as Fe, and Co on the electronic conduction is well known, it was unexpected to find a strong concentration dependent effect of dopants like Y3+ and Zr4+ in ceria or Mg2+ and Sr2+ in the gallates upon the electronic conductivity within the electrolytic domain. Ions like Y3+ and Zr4+ cause a shift and a partial broadening of electronic states in ceria based materials. Indications have been found for band tailing due to high defect concentrations. In some cases, the dopants cause the appearance of additional localized electron states in the gap which give rise to weak superimposed maxima of the electronic conductivity at a particular oxygen partial pressure within the electrolytic domain.

Accordingly, one cannot expect that electronic conductivities of solid electrolytes are insensitive to a changing concentration of stabilizers such as Y, Ca, etc. For instance, even a moderate doping of ceria by zirconia leads to a considerable electronic excess conductivity in the electrolytic domain.
Sensor Response of Stilbite Single Crystals Under “in Situ” Conditions
Authors: Schäf O. , Ghobarkar H. , Knauth P.
Published: April 2011

The isothermal conductivity of natural stilbite single crystals depends on water content, polar organic molecule concentration and charge compensating cation species. The observed interaction processes are almost completely adsorptive at temperatures below 110°C; catalytic oxidation of the organic molecules is taking place at much higher temperatures, where zeolitic water is almost completely desorbed. A schematic model describing the observed conductivity modifications is developed.
Characterizations of Core-Shell Nanoparticle Catalysts for Methanol Electrooxidation
Authors: Maye Mathew M. , Luo Jin , Chan Wai-Ben , Han Li , Kariuki Nancy , Naslund H. Richard , Engelhard Mark H. , Lin Yuehe , Sze Randoll , Zhong Chuan-Jian
Published: April 2011

This paper describes the results of an investigation of the structure and composition of core-shell gold and alloy nanoparticles as catalytically active nanomaterials for potential fuel cell catalysis. Centered on the electrocatalytic methanol oxidation, we show three sets of results based on electrochemical, surface, and composition characterizations. First, electrochemical studies have revealed that the nanostructured catalysts are active towards the electrooxidation of methanol and carbon monoxide. Second, X-ray photoelectron spectroscopy (XPS) data have shown that the organic encapsulating shells can be effectively removed electrochemically or thermally, which involves the formation of oxides on the nanocrystals. Thirdly, direct current plasma - atomic emission spectrometry (DCP-AES) has revealed insights for the correlation of the composition of alloy nanoparticles with the catalytic activities. Implications of these results to the design of nanostructured catalysts will also be discussed.
Effective Hydrogen Separation Using Ion Beam Modified Polymeric Membranes
Authors: Coleman M. R. , Xu X. , Ilconich J. , Ritchie J. , Hu L.
Published: April 2011

High purity H2 gas streams are increasingly important for a variety of applications including feed gases for fuel cells. The potential of hydrogen gas as primary energy source has generated considerable interest in hydrogen separation technologies. We have been investigating ion beam irradiation as a method to modify polymeric membranes to enhance both hydrogen permeability and permselectivities. Combined high permeabilities and permselectivities are required to give high recoveries of high purity hydrogen. Ion irradiation typically results in the formation of numerous crosslinks within the polymer matrix that should enable these materials to maintain selectivities at high temperatures and to resist chemical attack. Helium separations over a range of temperatures of irradiated polyimides were used as a model of the hydrogen system. Finally, the impact of irradiation conditions on gas separations in these materials will be addressed.
Spontaneous spirals in vibrated granular chains
Authors: Ecke R. E. , Daya Z. A. , Rivera M. K. , Ben-Naim E.
Published: April 2011

We present experimental measurements on the spontaneous formation of compact spiral structures in vertically-vibrated granular chains. Under weak vibration, when the chain is quasi two-dimensional and self-avoiding, spiral structures emerge from generic initial configurations. We compare geometrical characteristics of the spiral with that of an ideal tight spiral. Globally, the spiral undergoes a slow rotation such that to keep itself wound, while internally, fast vibrational modes are excited along the backbone with transverse oscillations dominating over longitudinal ones. Spirals have an extremely small volume in phase space, and hence, their formation demonstrates how nonequilibrium dynamics can result in a nonuniform sampling of phase space.

PACS numbers: 81.05.Rm, 83.10Nn
Using Interdisciplinary Examples in Nanotechnology to Teach Concepts of Materials Science and Engineering
Authors: Crone Wendy C. , Payne Amy C. , Zenner Greta M. , Ellis Arthur B. , Lisensky George C. , Condren S. Michael , Lux Ken W.
Published: April 2011

The National Science Foundation-supported Materials Research Science and Engineering Center (MRSEC) on Nanostructured Materials and Interfaces at the University of Wisconsin – Madison has an extensive education and outreach effort. One theme of this effort is the development of instructional materials based on cutting-edge research in nanoscale science and engineering. The Nanoworld Cineplex contains movies and demonstrations that can be brought into classes, and the Nanotechnology Lab Manual contains numerous experiments that can be used for virtual or actual laboratories. Also available are kits, software, teaching modules and articles. A hands-on kit for nontechnical audiences, “Exploring the Nanoworld,” has been produced in collaboration with the Institute for Chemical Education.

In this paper, novel hands-on demonstrations and innovative laboratory experiments aimed at the college level will be highlighted. High-tech devices and materials such as light emitting diodes (LEDs), shape memory alloys, amorphous metal, and ferrofluids are discussed in the classroom and studied in the laboratory as illustrations of nanotechnology and its impact on energy, the environment and our quality of life. These examples illustrate interdisciplinary research that provides connections among materials science, chemistry, physics, engineering, and the life sciences. They also highlight the tools of nanotechnology, such as scanning probe microscopy, electron microscopy, x-ray diffraction, and chemical vapor deposition, which are associated with the preparation and characterization of nanostructured materials. Demonstrations of the incorporation of nanotechnology to teach fundamental materials science principles presented are summarized at http://www.mrsec.wisc.edu/edetc.
PUI/MRSEC Collaboration to Create Opportunities for Women in Materials-Research
Authors: Goldberg Velda , Kaplan Michael , Soltzberg Leonard
Published: April 2011

This three-year collaboration between a predominately undergraduate women's college (Simmons College) and a NSF-supported Materials Research Science and Engineering Center (the Cornell Center for Materials Research (CCMR)) focuses on establishing a collaborative Simmons/Cornell research program that provides opportunities for students to work with faculty on timely research projects, have access to sophisticated instrumentation, and gain related work experience in industrial settings. To interest women in participating in materials-related research and to encourage them to consider further career exploration in this area, the secondary goal of the project focuses on augmenting women's undergraduate experience. In this regard, the project uses the PUI/MRSEC collaboration to enhance the undergraduate curriculum at Simmons and encourage new Ph.D.s in materials-related disciplines at Cornell to consider academic careers at Primarily Undergraduate Institutions (PUIs).

To provide opportunities for students to work on research throughout their undergraduate careers, this program focuses on studying the degradation processes in organic light emitting diodes (OLEDs). These materials are currently of great interest for display applications, and an understanding and control of the degradation processes could ultimately influence their use in various types of consumer products.

To widen science students' exposure to materials science, a new minor in materials was developed and materials science topics are being incorporated into physics and chemistry courses. To encourage students to consider graduate or industrial careers in materials science and to ease the transition into these large research environments, CCMR will place students in summer industrial jobs and REU positions. To provide students with further access to sophisticated instrumentation, a portion of the laboratory requirement for the new minor in materials will be co-taught during the summer by Simmons and Cornell collaborators at CCMR's Shared Experimental Facilities. Cornell's graduate students will participate in the program as mentors for Simmons undergraduates and will visit Simmons to better understand postgraduate teaching careers at PUIs.
Assembly of Gold Nanoparticles on DNA Strands
Authors: Noyong Michael , Gloddek Kirsten , Simon Ulrich
Published: April 2011

In this work we report first results on a direct deposition of 2–4nm gold nanoparticles onto DNA strands. In a two step protocol first cis-Pt (cis-diamminedichloroplatinum(II), cis-Pt(NH3)2Cl2) is intercalated into a DNA duplex. In a second step cysteamine stabilized gold nanoparticles are immobilized on DNA due to a ligand exchange (NH3 vs. NH2-R) at the Pt center which was done in solution as well as on surface bound oligonucleotides. The DNA-nanoparticle assemblies are prepared on mica and silicon and are imaged by AFM.
Low Sintering Temperature of CuO-Fluxed Ag(Nb, Ta)O3 Dielectric Ceramics
Authors: Wang Chiping , Shrout Thomas , Yang Gaiying , Kim Hyo-Tae , Kwon Do-Kyun , Lanagan Michael T.
Published: April 2011

Solid solutions in the Ag(NbxTa1−x)O3 (where 0 ≤ × ≤ 1) system exhibit excellent dielectric properties at microwave frequency including high dielectric constant (200<k<400), low loss (tanΔ ∼ 0.004) and a composition controlled temperature coefficient of capacitance (TCC). For Ta-rich and Nb-rich solid solutions, the TCC values are negative and positive, respectively, and two-phase mixtures provided an average TCC close to zero. Series, parallel, and logarithmic mixing rules were applied to predict dielectric constant and TCC of polyphase assemblages (45wt%Ag(Nb0.65Ta0.35)O3+55wt% Ag(Nb0.35Ta0.65)O3) yielded an average dielectric constant of 450 and a TCC of 180ppm/°C. Microstructure analysis revealed that a CuO-rich liquid remains at the grain boundary and transmission electron microscopy shows that the CuO resides at triple points. Ag(NbxTa1−x)O3 ceramics were successfully integrated into LTCC for embedded capacitors. The addition of CuO lowered the sintering temperature to below 900°C and a low TCC was maintained for fine grained microstructures.
Cu-Compatible Ultra-High Permittivity Dielectrics for Embedded Passive Components
Authors: Ihlefeld Jon F. , Kingon Angus I. , Borland William , Maria Jon-Paul
Published: April 2011

Barium titanate thin films have been prepared by chemical solution deposition on 18 μm thick, industry standard copper foils in the absence of chemical barrier layers. The final embodiment exhibits randomly oriented BaTiO3 grains with diameters between 0.1 and 0.2 μm, and an equiaxed morphology. The average film thickness is 0.6 μm and high resolution cross sectional microscopy shows no indication of interfacial phases. The BaTiO3 films are sintered in a high temperature reductive atmosphere such that copper oxidation is avoided. Subsequent lower-temperature, higher oxygen pressure anneals are used to minimize oxygen point defects. Permittivities greater than 3000 are observed, with loss tangents under 2.5%. The BaTiO3 phase exhibits pronounced ferroelectric switching and coercive field values near 20 kV/cm. Temperature dependent measurements indicate a ferroelectric transition near 100 °C with very diffuse character. Combining the approaches of the multilayer capacitor industry with traditional solution processed thin films has allowed pure barium titanate to be integrated with copper. The high sintering temperature – as compared to typical film processing – provides for large grained films and properties consistent with well-prepared ceramics. Integrating BaTiO3 films on copper foil represents an important step towards high capacitance density embedded passive components.
Improvement of Tantalum Pentoxide Metal-Insulator-Metal Capacitors For SiGe RF-BiCMOS Technology
Authors: Sun Hongjiang , Lau Ka Man , Aksen Eyup , Bell Nancy
Published: April 2011

Improvement activities were made in fully integrated Metal-Insulator-Metal (MIM) capacitors (>5fF/μm2) used in the advanced SiGe RF BiCMOS technology. By changing the process sequence of the lower metal electrode and the MIM capacitor, an improved MIM capacitor has achieved a lower leakage density with a better voltage linearity at 27°C − 150°C temperature range and a lower temperature dependency from −6V to +6V. Voltage coefficients VC1 and VC2 are 187ppm/V and 24ppm/V2 respectively, and temperature coefficient of capacitance TC1 is 99 ppm/°C with a negligible TC2. The leakage current density is 3.1×10−3 A/cm2 at 125°C for 5.5V with a breakdown voltage of 20V.

To increase capacitance density while maintaining low leakage, an ozone treatment after tantalum pentoxide film deposition has been investigated. A capacitance density as high as 10.3fF/μm2 has been achieved with a leakage density one order lower than the standard process. The fact that the extracted dielectric constant increased from 28 to 32 as well as the significant changes of the voltage and temperature coefficients clearly indicated that the ozone treatment has changed the intrinsic property of the tantalum pentoxide film as well as the top dielectric surface.
Preparation and Use of Chip Capacitors in Ultra-Dense Multi-Chip Modules
Authors: Pryputniewicz D. , Kondoleon C. , Haley J. , Marinis T.
Published: April 2011

Draper Laboratory designs and produces ultra-dense multi-chip modules that achieve an integration density, which is only exceeded by that of custom ASIC chips. These modules are fabricated by tiling an adhesive coated substrate with bare integrated circuit chips and passive components that are thinned to 150 microns thick. Multiple layers of thin film copper conductors, supported on Kapton film dielectric, are used to route signals between these components. Connections to their I/O pads and between signal layers are made through laser drilled vias, which are copper plated. The various types of capacitors used in modules for RF applications present several fabrication challenges. In comparison to active IC devices, capacitors have wider dimensional tolerances, are more easily damaged by mechanical handling, and are more susceptible to damage during laser drilling of vias. This paper will discuss these issues and the approaches that have been taken to address them.
Crystallization of Sub-100 nm-Thick Bi4-xLaxTi3O12 Films on Silicon Substrates and Their Electrical Properties
Authors: Kohno Atsushi , Ishitsu Fumitake , Matuo Kazuhiro , Tomari Hiroyuki
Published: April 2011

Polycrystalline Bi4-xLaxTi3O12 (BLT) thin films were formed on p-Si(100) substrates. Crystallization of the film was investigated quantitatively by X-ray diffraction (XRD) and X-ray reflection (XRR) analyses. The film was crystallized onto bismuth-oxide layered perovskite structure when annealing temperatures became higher than 550°C. The annealing time dependence of diffraction intensity and peak width indicated that grain growth occurred during crystallization. Moreover, it was shown that the average crystal dimension in the BLT film reached ca. 60 nm by 120-min annealing. That value is comparable to the B LT thickness. Film thickness and density were evaluated by XRR analysis. Simulation fitting showed that the BLT film was densified and that an interfacial layer was formed during crystallization. Pole figure measurements also suggested that the c-axis of B LT was preferentially oriented to nearly parallel the surface. Clockwise hysteresis loops were observed at room temperature in capacitance-voltage (C-V) characteristics of Au/BLT/p-Si structures. The coercive field and the dielectric constant of 65 nm-thick BLT films crystallized at 550°C for 60 min were evaluated to be ca. 23 kV/cm and ca. 17, respectively.
Ferroelectric property of an epitaxial lead zirconate titanate thin film deposited by a hydrothermal method
Authors: Morita Takeshi , Wagatsuma Yasuo , Cho Yasuo , Morioka Hitoshi , Funakubo Hiroshi , Nava Setter
Published: April 2011

Hydrothermal method has various advantages; low deposition temperature, high-purity, deposition on a three-dimensional structure and a large thickness. Although epitaxial PZT thin film deposition has reported, ferroelectric measurement has not been conducted due to the peel-off morphology of the film. The present paper investigates the improvement of an epitaxial PZT thin film deposited via a hydrothermal method. By adjusting the position at which the substrate was suspended in the solution, smooth morphology surface was successfully obtained. As a bottom electrode, 200 nm SrRuO3 thin film was deposited on SrTiO3 single crystals, and the PZT thin was deposited on SrRuO3. The remanent polarization 2Pr for PZT on SrRuO3/SrTiO3 (001) was 19.5 μC/cm2 and that of PZT on SrRuO3/SrTiO3 (111) was 37.2 μC/cm2 respectively. The self alignment poling direction was confirmed via scanning nonlinear dielectric microscopy and is thought to have been related to the deposition mechanisms.
Hydrothermally Deposited PZT Thin Films With Vertically Oriented Columnar Growth
Authors: Solberg Scott , Rodkin Alexandra , Xu Baomin , Littau Karl
Published: April 2011

A novel growth mode for hydrothermal films of lead zirconate titanate (PZT) has been discovered. Previously reported hydrothermal PZT films have had a loosely-packed cubic morphology, and indeed that is the most common growth mode. However, under special growth conditions, with much more dilute reagent concentrations than previously reported, substantially vertically oriented, long rod shaped grains may be grown. Metal-organic reagents such as lead acetate trihydrate, zirconium propoxide, and titanium isopropoxide were used along with potassium hydroxide mineralizer. Metal and metal-coated substrates with appropriate perovskite seed layers, such as lead titanate (PT) and PZT were used. Unlike other film deposition methods, such as sputtering, MOCVD, or sol-gel, which typically require greater than 500°C processing temperatures, the hydrothermal processes described in this report allowed the growth of highly crystalline films at temperatures as low as 120°C. The unique vertical rod-like ferroelectric films may be useful in electrical devices such as capacitors.
First Prototype of High-Density Ferroelectric Data Storage System
Authors: Hiranaga Yoshiomi , Cho Yasuo , Wagatsuma Yasuo
Published: April 2011

The first prototype of high-density ferroelectric data storage system based on scanning nonlinear dielectric microscopy was developed in order to establish basic elemental technologies for actual read/write functions aiming for practical application. Using this system, a data transfer rate was evaluated. 9 kbps reading and 50 kbps writing were demonstrated with respect to 440 kbit/inch bit data array written on a lithium tantalate single crystal thin plate. Additionally, we considered future prospects for developing the data storage system with further fast data transfer rate.
A Transmission Electron Microscopy Study of Dislocation Substructures in PLD-grown Epitaxial Films of (Ba,Sr)TiO3 on (001) LaAlO3
Authors: Misirlioglu I. B. , Vasiliev A. L. , Aindow M. , Ramesh R. , Alpay S. P.
Published: April 2011

Epitaxial Ba0.6Sr0.4TiO3 films were grown onto (001) LaAlO3 by pulsed-laser deposition, and the dislocation structures of the films were investigated using transmission electron microscopy. Misfit dislocations with a periodicity of about 7 nm and Burgers vectors b = a<100> were observed at the interface. High densities of threading dislocations was present in the films with Burgers vector b = a<100>. The observations reveal that threading dislocations are not generated as the result of half-loop climb from the deposit surface as proposed previously, but are instead formed when misfit dislocations are forced away from the interface during island coalescence.
Magnetostriction of Field-Structured Composites
Authors: Martin James E. , Anderson Robert A. , Gulley Gerald
Published: April 2011

Field-structured magnetic particle composites are an important new class of materials that have great potential as both sensors and actuators. These materials are synthesized by suspending magnetic particles in a polymeric resin and subjecting these to magnetic fields while the resin polymerizes. If a simple uniaxial magnetic field is used, the particles will form chains, yielding composites whose magnetic susceptibility is enhanced along a single direction. A biaxial magnetic field, comprised of two orthogonal ac fields, forms particle sheets, yielding composites whose magnetic susceptibility is enhanced along two principal directions. A balanced triaxial magnetic field can be used to enhance the susceptibility in all directions, and biased heterodyned triaxial magnetic fields are especially effective for producing composites with a greatly enhanced susceptibility along a single axis. Magnetostriction is quadratic in the susceptibility, so increasing the composite susceptibility is important to developing actuators that function well at modest fields. To investigate magnetostriction in these field-structured composites we have constructed a sensitive, constant-stress apparatus capable of 1 ppm strain resolution. The sample geometry is designed to minimize demagnetizing field effects. We have demonstrated field-structured composites with nearly 10,000 ppm strain, and have shown that at large magnetic fields a structural phase transition occurs within the composite. These experimental results are compared to microscopic, self-consistent field simulations of magnetostriction in these complex, disordered materials.
ZnO Based SAW Delay Line: Thin Film Characteristics and IDT Fabrication
Authors: Hassani Farid , Ahmadi Shahrokh , Korman Can E. , Zaghloul Mona , Hullavarad Shiva , Vispute R.D. , Venkatesan T.
Published: April 2011

ZnO, a well-known piezoelectric material, is used to develop micro-scale Surface Acoustic Wave (SAW) delay line sensor. In this work, SAW delay line Devices are fabricated employing ZnO films that are deposited by RF sputtering technique. Films are characterized prior to device fabrication by X-Ray Diffraction (XRD) for film crystalline quality, UV-visible transmission spectroscopy for optical characteristics, and Atomic Force Microscopy (AFM) for surface morphology. Interdigital electrodes producing surface acoustic waves in the hundreds of MHz are developed by photolithography and metalization techniques. SAW delay line device testing, measurement and characteristics on RF sputtered ZnO films are presented and compared.
Dielectric Properties and Long-Range Structural Order in (x)Pb(In1/2Nb1/2)O3:(1-x)Pb(Mg1/3Nb2/3)O3 Relaxor Ceramics
Authors: Tai C. W. , Baba-kishi K. Z.
Published: April 2011

The relative permittivity of (x)Pb(In1/2Nb1/2)O3:(1-x)Pb(Mg1/3Nb2/3)O3 ceramics with compositions x=0.1, 0.3 and 0.6 were found to exhibit relaxor behavior. The maximum values of the relative permittivity at 100 Hz were ∼ 6500 at -2°C, 4000 at 5°C and 3700 at 15°C for x=0.1, 0.3 and 0.6, respectively. The 1:1 structural long-range ordering and forbidden reflections were studied by transmission electron microscopy. The size of the ordered domains increased with increasing Pb(In1/2Nb1/2)O3. In addition to the superstructure reflection 1/2 1/2 1/2, the forbidden reflection 1/2 1/2 0 and streaking were observed.
Silicide Formation at HfO2/Si and ZrO2/Si Interfaces Induced by Ar+ Ion Bombardment
Authors: Lebedinskii Yu. , Zenkevich A. , Filatov D. , Antonov D. , Gushina J. , Maximov G.
Published: April 2011

The effect of ion bombardment with Ar+ at the energy E=2.5 keV on HfO2/Si and ZrO2/Si interfaces has been investigated in situ with XPS by growing thin metal oxide layers and further ion etching them. It is shown that a silicide layer ∼2 nm in thickness is forming, and Ar+ ion beam affects MeO2/Si (Me=Hf, Zr) interface at thickness ≤3 nm. Ex situ AFM/STM corroborates the formation of silicide layer at metal oxide/silicon interface.
Characterization of High-k Dielectrics by Combined Spectroscopic Ellipsometry (SE) and X-Ray Reflectometry (XRR)
Authors: Sun L. , Defranoux C. , Stehle J.L. , Boher P. , Evrard P. , Bellandi E. , Bender H.
Published: April 2011

At present, new high-k dielectric materials are being intensively investigated to replace the silicon dioxide as gate dielectric for the next generation of electronic devices. Several candidate materials (such as ZrO2, HfO2, Al2O3) and deposition processes are currently under investigation. Because the layer thickness which is required in the next generations of devices is of the order of few nanometers, a precise determination and control of layer thickness will be mandatory. Although spectroscopic ellipsometry (SE) is well established non-contact, non-destructive and precise technique for determining thickness and optical properties of thin films, it becomes more difficult to obtain this information unambiguously and simultaneously for ultra-thin films with traditional SE alone because of possible high correlations between film structure and optical properties. The grazing x-ray reflectometry (XRR) is a complementary nondestructive optical technique and can be used to unambiguously determine ultra thin film thickness accurately. Combined with ellipsometry technique together, it will provide a promising way to characterize high-k gate dielectrics including thickness, roughness, interfacial layers and material composition information etc. In this paper, the principles for both SE and XRR will be briefly reviewed and limitation of each technique will be discussed. Following the high-k gate dielectric exploration and development, examples of using the combined SE/XRR techniques will be presented.
Atomic Layer Deposition of Silica and Group IV Metal Oxides Nanolaminates
Authors: Zhong Lijuan , Chen Fang , Campbell Stephen A. , Gladfelter Wayne L.
Published: April 2011

With alternating exposure of Si (100) substrates to tri (t -butoxy) silanol and anhydrous zirconium nitrate, mixed films of zirconia and silica were deposited at 162°C. The films were atomically smooth and their thickness was uniform across the entire substrate. The maximum growth rate of 12 Å/cycle implies deposition of more than one monolayer per cycle. A singular reflection in the low angle X-ray scattering pattern indicates an ordered bi-layer structure. Similar nanolaminate structures were also formed using anhydrous nitrates of hafnium and tin.
Atomic Scale Modeling of ZrO2 and HfO2 Atomic Layer Deposition on Silicon: Linking Density Functional Theory and Kinetic Monte Carlo
Authors: Estève A. , Jeloaica L. , Mazaleyrat G. , Dkhissi A. , Djafari Rouhani M. , Ali Messaoud A. , Fazouan N.
Published: April 2011

The present paper establishes some required elements from both Quantum calculations and Kinetic Monte Carlo Modeling to perform full atomic scale simulations of Zirconia and Hafnia Atomic Layer Deposition (ALD) on Silicon technology process. In this view, we present quantum cluster calculations that investigate reaction pathways being part of the chemical reactions taking place at the different stages of the ALD growth. In particular, we detail ongoing research effort on the hydrolysis of adsorbed HfCl3 and ZrCl3 on ultra-thin SiO2. At very low water dose, the hydrolysis appears to be un-favourable. The complete reaction pathways with their associated activation barrier are detailed. We then show that actual available mechanisms emanating from quantum calculations are not sufficient to give a coherent picture of the layer structuring through a Kinetic Monte Carlo technique with the hope of giving new directions for further quantum studies.
Electronic structure of Zn(Mn)O surface alloy - a resonant photoemission study
Authors: Guziewicz E. , Kopalko K. , Sadowski J. , Guziewicz M. , Golacki Z.
Published: April 2011

Electronic structure of Mn/ZnO system has been investigated by synchrotron radiation photoemission. Manganese vacuum deposition was done at room temperature onto a ZnO(0001) single crystal for coverage ΘMn < 4 ML. Photoemission spectra taken near Mn3p-Mn3d absorption edge after each deposition step show resonant enhancement of Mn3d states within 10 eV of the Fermi level. The experimentally deduced partial Mn3d density of states for Θ > 1.2 ML shows at least three features: a major Mn3d structure at 3.8–4.5 eV below the Fermi energy, a valence structure at lower binding energy (1–3 eV) and a broad satellite in the 5.5 – 9 eV range. The branching ratio of satellite/main structure increases with deposition from 0.33 for 0.4 ML to 0.65 for 4 ML. After annealing up to 500 C the satellite/main ratio decreases to 0.43 indicating a high degree of hybridization between the Mn3d states and valence band of ZnO. After annealing no manganese cap layer was found at the crystal surface as was confirmed by the lack of metallic Fermi edge in photoemission spectra and by scanning Auger spectroscopy experiment. The photoemission Mn3p core level spectra taken after annealing consist of two components separated by about 4eV. It is evidence that at least two manganese states are observed in the Mn-ZnO interface region.
Photo- and Thermal Annealing-Induced Processes in Carbon Nanotube Transistors
Authors: Shim Moonsub , Siddons Giles P. , Jeong Jae Kyeong , Merchin David
Published: April 2011

Photoinduced conductivity changes and effects of thermal annealing in carbon nanotube transistors have been examined. Low-intensity ultraviolet light significantly reduces the p-channel conductance while simultaneously increasing the n-channel conductance. A combination of optical absorption and electron transport measurements reveals that these changes occur without variations in dopant concentrations. Measurements with different metals reveal that UV induces oxygen desorption from the electrodes rather than from nanotubes. In Ti-nanotube contact where the Schottky barrier plays an important role, photodesorption of oxygen mainly occurs from the native oxide of Ti electrodes. Decrease in the p-channel conductance arises from the metal work function change which causes larger hole Schottky barrier. Non-Schottky Pd-contacted nanotube transistors do not show photodesorption effects with low intensity UV. Thermal annealing of nanotube transistors with Ti/Au electrodes also leads to the disappearance of the photodesorption effects. However, a noticeable p-doping is observed to upon air exposure after thermal annealing.
Observation of Size Confinement Effects of Excitons in AgX Nanocrystals by Cryo-Energy-Filtering TEM/EELS
Authors: Oleshko Vladimir P.
Published: April 2011

The non-uniform size-dependent contrast of AgBr0.95I0.05 nanocrystals (NCs) ranging from 22 to 80 nm in equivalent diameter (dc) observed by cryo-energy-filtering TEM is referred to predominant excitations at the surfaces and near the edges. When the fields due to surface losses reach throughout the structure, they couple and the probability for their generation becomes periodic in the NC size. Since electronic sum rules must be satisfied, the surface excitations reduce the strength of the bulk excitations. Coupling of surface and volume losses may cause oscillations of the image intensities with the NC size. The appearance of such oscillations demonstrates a size confinement of excitations of valence electrons due to contributions to the energy-level structure from carrier confinement and surface states. The imaginary part of relative dielectric permittivity derived from electron energy-loss spectra shows an enhanced intensity of the band at 4 eV for NCs with dc = 50±4 nm as compared to those of 109±7 nm in size, while the bands at 7 eV and at 10 eV appear to be suppressed. An increase of the intensity of exciton-assisted direct interband transition at 4 eV (Γ8-, Γ6- → Γ6) correlates with the size-dependent enhancement of free exciton luminescence from AgBr NCs, when their size is less than 100 nm.
Crystallographically-Oriented Electrochemically-Deposited Bismuth Nanowires
Authors: Rabin Oded , Chen Gang , Dresselhaus Mildred S.
Published: April 2011

Bismuth nanowires 200 nm in diameter were synthesized via electrochemical deposition into the pores of anodic alumina templates. A near neutral pH solution and a special sample holder were employed. Both polycrystalline and (012) oriented bismuth nanowire arrays were prepared. The electrical resistance of the samples versus temperature was measured in the range 2–300 K, and the results were fitted to a transport model. Despite the crystallographic alignment of the nanowire array, the model calculations suggest the dominance of a temperature independent scattering mechanism (such as grain boundary or nanowire boundary scattering). The results are compared to the electrical resistance of nanowires formed by impregnation techniques.
Effect of K/Bi ordering on the electronic structure of K2Bi8Se13
Authors: Bilc Daniel I , Larson Paul , Mahanti S.D. , Kanatzidis M.G.
Published: April 2011

K2Bi8Se13 belongs to a class of complex chalcogenides which show potential for superior thermoelectric performance. This compound forms in two distinct phases, α and β. The β-phase, which has several sites with mixed K/Bi occupancy is a better thermoelectric. To understand the origin of this difference we have carried out electronic structure calculations within ab initio density functional theory using full potential linearized augmented plane wave (FLAPW) method. The generalized gradient approximation was used to treat the exchange and correlation potential. Spin-orbit interaction (SOI) was incorporated using a second variational procedure. The α-phase is found to be a semiconductor with an indirect band gap of 0.47eV compared to 0.76eV for the observed direct optical gap. For the β-phase we have chosen two different ordered structures with full occupancies of K and Bi atoms at the “mixed sites”. The system is a semi-metal for both the ordered structures. To incorporate the effect of mixed occupancy we have chosen a 1x1x2 supercell with an alternative K/Bi occupancy at the “mixed sites”. The superlattice ordering gives a semiconductor with an indirect gap of 0.38eV. Mixed occupancy is crucial for the system to be a semiconductor because the Bi atoms at the “mixed sites” stabilize the p orbitals of the neighboring Se atoms by lowering their energy, and opening up a gap at the chemical potential.
Extended Huckel electronic calculations for PrFe4P12
Authors: Galvan D. H. , Samaniego J. C.
Published: April 2011

Electronic structure calculations were performed on PrFe4P12 filled skutterudite, in order to provide more information regarding its properties. The energy bands yielded information regarding the metallic behavior as well as a mini gap of 0.02 eV. Total and projected Density of States (DOS) yielded information for the existence of a hybridization between Pr -f, Fe -d and P -p orbitals. Hence, this compound could be considered a likely candidate as a thermoelectric compound.
Irreversible Tensile Stress Development in PECVD Silicon Nitride Films
Authors: Hughey Michael P. , Cook Robert F.
Published: April 2011

The thermo-mechanical behavior of plasma-enhanced chemical vapor deposited (PECVD) silicon nitride films are investigated during thermal cycling and annealing. It is well known that PECVD films have a large amount of incorporated hydrogen that evolves on heating. This reduction in hydrogen is shown to be directly responsible, via constrained volume decrease, for irreversible increases in tensile stress. It is demonstrated that no stress equilibrium is attained during very long time anneals. The thermal cycling behavior of PECVD films can be modeled by chemical reaction theory, with the irreversible development of film stress a mechanical consequence. The model assumes first-order reaction kinetics of Si-H and N-H bonds, which react to form molecular hydrogen and reformed network bonds. The activation energy of reaction is not single-valued, indicative of the strong influence that the local bonding environment has on bond energies. If the incorporated hydrogen reactant pairs are assumed to be normally distributed with activation energy, irreversible stress development is well modeled, and the mean activation energy ranges from 2.44 to 2.93 eV for 150 to 300 °C deposited films.
Solutions and Discussions of thin film Undergoing the Nonlinear Peeling
Authors: Wei Yueguang , Shu Siqi , LNM Ying Du
Published: April 2011

Based on the bending model, three double-parameter criteria characterizing thin film peeling process are introduced and analyzed in detail. Three double-parameter criteria include: (1) the interfacial fracture toughness and the separation strength, (2) the interfacial fracture toughness and the interfacial crack tip slope angle of thin film, and (3) the interfacial fracture toughness and the critical von Mises effective strain of thin film at crack tip. Based on the three double-parameter criteria, the thin film nonlinear peeling problems are solved analytically for each case. The results show that the solutions of thin film nonlinear peeling based on the bending model are very sensitive to the model parameter selections. Through analyses and comparisons for different solutions, a connection between solutions based on the bending models and based on the two-dimensional elastic-plastic finite element analysis is obtained.
Stress-assisted Copper-induced Lateral Growth of Polycrystalline Germanium
Authors: Hekmatshoar B. , Shahrjerdi D. , Mohajerzadeh S. , Khakifirooz A. , Robertson M. , Afzali-Kusha A.
Published: April 2011

Lateral growth of poly-Ge at temperatures as low as 150°C is reported. External mechanical stress has been properly manipulated to drive the low temperature Cu-induced crystallization of poly-Ge wherever Cu is deposited to form the crystallization seed for lateral growth. Uniaxial compressive stress has been externally applied to the Ge layer by bending the flexible PET substrate inward. A 10-hour period thermo-mechanical post-treatment in the presence of 0.05% equivalent compressive strain leads to a growth rate of 2.5 μm/hour in the direction of the applied stress and 1.8 μm/hour in the perpendicular direction, as confirmed by SEM analysis. We believe that partial growth of the Cu-seeded poly-Ge region in the form of tetragonal structures is the key feature which leads to the lateral growth of the pure-Ge strip. Elimination of the compressive stress hinders the lateral growth completely, even at reasonably high temperatures.
Microstructural aspects of fracture in nanolayered TiAlCrN thin films
Authors: Santana A. E. , Karimi A. , Derflinger V. H. , Schütze A.
Published: April 2011

This paper studies the effects of bilayer thickness and chromium content on the microstructure and mechanical properties of nanolayered TiAlN/CrN thin films. By rotation of samples holder and control of targets activity, a variety of multilayers and chemically modulated thin films were grown on WC-Co substrates using cathodic arc PVD. Conventional and high resolution TEM showed that aluminum contributes to refinement of structure while chromium favors the formation of coarse columnar morphology. Consequently, TiAlN layers periodically interrupt the formation of columns in CrN layers in multilayer films, while in chemically modulated samples the columns are not interrupted leading thus to the formation of strongly columnar films. Both Cr content and bilayer thickness contribute to hardness enhancement. Effect of Cr arises from the formation of hard fcc-(CrAl)N phase to the detriment of softer wurtzite-like hcp-AlN. The contribution of bilayer thickness is explained by the grain refinement based on Hall-Petch effect and the formation of highly stressed columnar structures with (111) preferred orientation. Such structural modifications strongly influence crack modes and morphologies as observed using AFM and FIB cross-section of indents. Thin bilayer films exhibit well-organized straight cracks parallel to the contact edge between indenter and film, while large bilayer films show a network of discontinuous irregular mud cracks attributed to grain boundary sliding. Refinement of structure favours crack meandering and branching that prevents the propagation of large cracks with more dramatic effects.
Microstructure Evolution of On-substrate NiTi Shape Memory Alloy Thin Films
Authors: Wang Xi , Lai Ann , Vlassak Joost J. , Bellouard Yves
Published: April 2011

When deposited at room temperature, sputtered NiTi thin films are amorphous and need to be crystallized before they can be used as a functional material. We present the results of an annealing study on substrate-constrained NiTi shape memory thin films. Amorphous films of a NiTi shape memory alloy were deposited by UHV sputtering. Films of thickness 1.0 μm were grown on (100) Si wafers both with and without an LPCVD SiNx barrier. The as-deposited films were annealed in vacuum at temperatures ranging from 500°C to 800°C. The microstructure of the annealed films was characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and Rutherford back scattering (RBS).
Growth of crack-free GaN on AlN quantum dots on Si(111)substrates by MOCVD
Authors: Sun W. H. , Chen J. L. , Wang L. S. , Chua S. J.
Published: April 2011

AlN self-assembled quantum dots (QDs) with high density of ∼ 4.4 × 1010/cm2 on Si(111) substrates have been grown by low-pressure chemical vapor deposition under a very low V/III ratio of 350. We found that using AlN-QD/AlN buffer two-inch GaN epilayers without cracks were grown, indicating the underlying quantum dots play a crucial role in relaxing the stain of GaN epilayer. The quality and morphology were investigated by atom force microscopy, transmission electron microscopy, X-ray diffraction and optical microscope.