bluuebunny/crossref_metadata_2025 huggingface dataset:
Organic Metals and Superconductors: Facile Synthetic Methodologies Bypassing Coupling and Chromatography
Authors: Meline Ronald L. , Elsenbaumer Ronald L.
Published: April 2011

The organic donor tetrathiafulvalene (TTF, 1) and its derivatives are synthesized from tetrathianaphthalene (TTN, 2) in a one pot reaction. The reaction takes advantage of an isomerization of lithiated TTN into lithiated TTF and subsequent substitution with novel disulfide electrophiles yielding substituted T donors. The isomerization approach eliminates the need for a chemical coupling reaction of oxones or thiones (a yield limiting procedure), and simple byproducts eliminate the need for tedious purification. The novel methodology allows for a high yield preparation of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF, 3a, 80%) and bis(propylenedithio)tetrathiafulvalene (BPDT-TTF, 3b), previously unavailable directly from TTF. A high yield of bis(phenylenedithio)tetrathiafulvalene (BPhDT-TTF, 3c, unavailable from dimercaptoisotrithione “DMIT”) is also achieved using the synthetic scheme. The method is general, and can be used to prepare a variety of novel organic donors based on TTF. Synthetic procedures along with all relevant characterization are presented.
Improved Electron Injection in Organic Light Emitting Devices by Applying Thin Insulating Layers
Authors: Pairleitner R. , Tasch S. , Leising G. , Scherf U.
Published: April 2011

We present the fabrication and characterization of organic light emitting devices (OLEDs) using thin insulating layers for improved electron injection. The OLEDs are constructed with an ITO anode and an aluminum cathode. For the active layer we use either ladder-type Polyparaphenylene (m-LPPP) or Parahexaphenyl (PHP). A thin film of an insulating material is applied between the active layer and the cathode, in order to achieve a better tunnel injection due to a higher electric field at the interface. We compared different insulating materials with various thickness. The best results are obtained by using a LiF-layer with a thickness between 10 Å and 15 Å. Thereby the onset voltage decreases and the current density in the device increases significantly.
Poly(2-Butyne-1,4-Diyl)S as Precursors to Novel Substituted Polyacetylenes
Authors: Pollack Steven K. , Fiseha Ashebir
Published: April 2011

Thermally-induced polymerization of 1,4-diphenyl-1,2,3-butatriene affords poly(1,4-diphenyl- 2-butyne-1,4-diyl) as a soluble high molecular weight material. Structure is characterized by 13C and vibrational spectroscopy. When treated with base, this material rearranges to a soluble red poly(acetylene) with a unique substitution pattern.
Deformed Helix Ferroelectric Liquid Crystals with Large Tilt Angles in Optically Addressed Spatial Light Modulators for Dynamical Holography Applications
Authors: Beresnev L. A. , Haase W. , Onokhov A. P. , Dultz W. , Isaev M. V. , Feoktistov N. A. , Ivanova N. L. , Konshina E. A. , Chaika A. N. , Berenberg V. A. , Weyrauch T.
Published: April 2011

Optically addressed spatial light modulators (OASLMs) based on deformed helix ferroelectric liquid crystals (DHFLC) with high tilt angles on order of 40° and helical pitches less than 0.2μm were developed. The diffraction efficiency reached the order of 20%. The light induced deviation of the optical axis of the DHFLC layer was measured in sandwich structures consisting of photoconductors and liquid crystals. The photoelectric parameters of photoconductive amorphous silicon carbide a-SiC:H and a photoconductive polymeric films were measured with and without light blocking and reflecting layers. The application of the developed OASLMs in a holographic image corrector was demonstrated.
Oxygen-Induced Inhibition of Noble Metal Silicide Formation: Implications for Electrode/Barrier Structures used with Perovskite Materials
Authors: Saenger K. L. , Grill A. , Kotecki D. E.
Published: April 2011

We describe how the inhibitory effect of ambient oxygen on suicide formation may be exploited in designing noble metal electrode structures suitable for perovskite-based memory devices. Reactions of Pt and Ir films with substrates of silicon and tungsten suicide (WSi2.8/Si) were examined after anneals in atmospheric pressure ambients of oxygen or nitrogen al temperatures of 640 °C for various initial noble metal film thicknesses. Metal/silicon reactions and phase formation were studied by Rutherford Backscattering Spectroscopy, X-ray diffraction. and electrical resistance measurements. While annealing in nitrogen resulted in complete noble metal silicidation in the all samples, some Pt and most to all of the Ir remained after equivalent anneals in oxygen. Oxygen exhibited a greater inhibitory effect on silicidation in thin Ir samples, where no suicide formation was observed. The consistent presence of unreacted noble metal M after oxygen annealing is attributed to the formation of an oxygen-containing M-O-Si barrier which interferes with the silicidation reaction. Qualitative through-film resistance measurements indicate that these in-situ formed M-O-Si barrier layers can be at least moderately conductive, a prerequisite for their possible use as a replacement for deposited barrier materials.
Microstructure Investigations and Structure-Property Correlations in Ferroelectric thin film Capacitors
Authors: Li H. , Yang B. , Dhote A. , Aggarwal S. , Salamanca-Riba L. , Ramesh R.
Published: April 2011

Epitaxial 0%, 3% and 10% La doped PZT capacitors with a LSCO bottom electrode grown by pulsed laser deposition on Si using a Ti(Al)N/Pt conducting barrier layer were systematically studied. Ferroelectric capacitors substituted with 10% La show a significantly lower coercive voltage compared to capacitors with 0% and 3% La. This is attributed to the systematic variation of the domain structure of the PLZT film with the increase of La concentration. The in-plane orientation relationship of this heterostructure is: [110]PLZT/[110]LSCO/[110]Pt/[110]Ti(AI)N[110]si. The morphology of the domains as a function of La concentration was studied using high resolution transmission electron microscopy(HREM). The Pt/Ti(Al)N conducting barrier layer stack is intact after the deposition of the LSCO/PLZT/LSCO stack. All Ti(Al)N layers in the samples studied consist of column-like structures with a [110] texture.
The Effects of the Addition of CF4, Cl2, and N2 TO O2 ECR Plasma on the ETCH Rate, Selectivity and Etched Profile of RuO2 Film
Authors: Lee Eung-Jik , Kim Jong-Sam , Kim Jin-Woong , Baik Ki-Ho , Lee Won-Jong
Published: April 2011

In this study, we investigated the effects of the addition of CF4, Cl2, and N2 gases to oxygen electron cyclotron resonance (ECR) plasma on the reactive ion etching (RIE) properties of RuO2 film such as etch rate, selectivity, and etched profile. The concentration of the etching species in the plasma was analyzed with an optical emission spectroscopy (OES) and a quadrupole mass spectrometer (QMS). The etch product was also examined with QMS.

The addition of a small amount of CF4, Cl2, or N2 to the O2 plasma increases the concentration of oxygen radicals and accordingly increases the etch rate of the RUO2 films appreciably. The etch rate of the RuO2 film was enhanced more with the addition of a small amount of CF4 and CI2 than with the addition of N2. On the contrary, the etched profile obtained in O2/N2 plasma was superior, without any damaged layer at the sidewall, to O2/CF4 and O2/Cl2 plasma. The selectivity of RuO2 to Si)2 mask was over 20:1 for each of the additive gas proportion at which the etch rate was maximum for each plasma system.
Characterization of Highly Textured PZT Thin Films Grown on LaNiO3 Coated Si Substrates by MOCVD
Authors: Lin C. H. , Yen B. M. , Chen Haydn , Wu T. B. , Kuo H. C. , Stillman G. E.
Published: April 2011

Highly textured PbZrxTi1−xO3 (PZT) thin films with x= 0-0.6 were grown on LaNiO3 coated Si substrates at 600 °C by metal-organic chemical vapor deposition (MOCVD). The preferred crystalline orientation of PZT thin films with various Zr concentration were characterized by X-ray diffraction (XRD). Microstructures were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The dielectric constants, hysteresis and fatigue behavior of these thin films were also measured. The relationship between growth rate and the preferential orientation is discussed. Furthermore, the dependence of the electrical properties on Zr concentration and preferential orientation is demonstrated.
Ir Electrodes for Ferroelectric Capacitors
Authors: Jung Sung Won , Bang Ilhwan , Lee Jaegab , Kim Jiyoung
Published: April 2011

In this study, Ir/IrO2 mixture electrodes are fabricated by furnace oxidation of sputter deposited Ir, IrO2 and their hybrid electrodes. The characteristics of furnace oxidation of various electrode stems with Ir family and their limitation are investigated. Annealing at higher than 700°C oxidation results in formation of undesirable extrusions in Ir electrode. When the Ir oxide facet extrusions are formed, Ir near at the extrusion is used up and SiO2 substrate are exposed. In addition, furnace oxidized Ir/Ti electrode is suggested as an alternative electrode, which shows smooth surface, good thermal stability, high oxygen contents and low resistivity.
Characterization of New SBT Sol System and its thin film on the Platinum Electrode for Fram Application
Authors: Choi YongSoo , Kim WooSik , Kim ChangEun , Yoo WhanSik , Kim BaeYeon , Song HanSang
Published: April 2011

Stable SBT sols for FRAM application were made from Sr-isopropoxide, Bi-acetate, and Ta-ethoxide with 2-ethoxyethanol as a solvent and chelating agent, TEA. The sol were spin-on coated on the Pt /Ti/SiO2/Si substrate. From the IR and DTA/TGA, the 2-ethoxyethanol -triethanolamine sol system is quite stable against aging. 5% excess Bi added sol and 800°C heat treatment of the thin film revealed the most crystallinity. There is a change in the orientation of thin film above 800°C heat treatment from c-axis to(105). The average grain size of thin film is very small, i.e., 40 nm at 800°C, and it has very narrow distributions, and the thickness of the coating were about 100nm, which would promise smaller electrode area and higher yield.
CMOS Compatible Integrated PZT Capacitors
Authors: Evans Joe T. , Boyer Leonard L. , Suizu Robert I. , Velasquez Geri
Published: April 2011

The fabrication of high yielding ferroelectric capacitors on CMOS wafers is difficult due to the negative impact of post-capacitor process steps, especially the interlayer dielectric and the metal interconnect sinter. Proper selection of the process for each layer of the capacitor structure is necessary to minimize hysteresis damage to the ferroelectric capacitors during their construction. The authors fabricated integrated PZT capacitors on blank silicon wafers using lift off processes for the bottom and top electrodes and a combination titanium dioxide/silicon dioxide dielectric between the ferroelectric capacitors and the metal interconnect layer. A 15 minute nitrogen anneal at 450 degrees centigrade after the metal interconnect patterning did not damage the capacitor hysteresis loops. Statistical testing of over 700 capacitors for shorts indicated a defect rate of 127 defects per square centimeter. This is sufficiently low enough to generate 50% yield in a production 64Kbit double-sided-sense nonvolatile memory. At 3.5V, the capacitors generated 14.0 microcoulombs per square centimeter with a standard deviation of 2.3 microcoulombs per square centimeter. The authors have set a target for future lots of 20 defects per square centimeter with 32 microcoulombs per square centimeter at 2.0V with a standard deviation of 1.6 microcoulombs per square centimeter.
Leakage Degradation in BST Dielectric Capacitors with Oxide and Metal Electrodes
Authors: Fukushima N. , Abe K. , Izuha M. , Kawakubo T.
Published: April 2011

Leakage degradation under DC stresses in epitaxially-grown Ba1−xSrxTiO3/SrRuO3 capacitors with various top electrodes was examined. Epitaxial capacitors employed in this study exhibit higher dielectric constant arising from optimized lattice deformation caused by lattice mismatch between Ba1−xSrxTiO3 and SrRuO3; dielectric constant for SrRuO3/30nm thick Bal-xSrxTiO3/SrRuO3 all oxide capacitor was 550, which corresponds SiO2 equivalent thickness of 0.21 nm. In addition, this type of capacitors have interfaces of higher cleanliness between dielectrics and electrodes, which are expected to provide opportunities of more simplified discussions on reliability issues for thin film capacitors. Dielectric breakdown properties and DC stress-induced leakage degradation properties were examined in room temperature and elevated temperatures. Various kinds of leakage degradation were observed and categorized in anode degradation and cathode degradation. The degradation in capacitors with oxide electrodes was markedly suppressed compared to that in capacitors with metal electrodes such as Pt or Ru. This higher degradation resistance yielded longer lifetime in capacitors of this type and the estimated life time at 458K for SrRuOS/ Bal-xSrxTiO3/SrRuO3 capacitor was 3E8 seconds, which exceeds required specification for DRAM application. These differences were discussed on the basis of a supposed degradation mechanism in which oxygen vacancy generation at anode interface is taken into account as well as vacancy accumulation at cathode interface.
Microstructure Control of (Ba, Sr)TiO3 Films for Gigabit Dram
Authors: Shen H. , Kotecki D. E. , Murphy R. J. , Zaitz M. , Laibowitz R. B. , Shaw T. M. , Saenger K. L. , Baniecki J. , Beitel G. , Klueppel V. , Cerva H.
Published: April 2011

(Ba, Sr)TiO3 films were deposited on Pt-coated SiO2/Si wafers by the MOCVD method. Experiments were conducted to investigate the mechanisms of nucleation and growth. It was observed that the diameter of the (Ba, Sr)TiO3 grains is established in the early stages of nucleation and does not increase substantially during the growth of the film. By controlling the process conditions, it is possible to control the final microstructure and improve the electrical properties of (Ba, Sr)TiO3 films. I-V and C-V measurements show that (Ba, Sr)TiO3 films with a thickness of approximately 15nm can produce a charge storage density of >120 fF/μm2 with a leakage current density of < 10 nA/cm2 at IV, making them suitable for Gigabit-scale DRAM applications.
Microwave Tuning Quality and Power Handling of Voltage-Tunable Capacitors: Semiconductor Varactors Versus Ba1−xSrxTiO3 Films
Authors: Gait D. , Rivkina T. , Cromar M. W.
Published: April 2011

Thin films of SrTiO3 and Ba0.4Sr0.6TiO3 have been pulse laser ablated onto LaAIO3 substrates. Normal metal coplanar capacitor electrodes were patterned on top of these films and the capacitors were incorporated into weakly coupled microstrip resonators. Resonant frequencies and Q's were measured as a function of bias at room temperature and at 77 K. The microwave frequency capacitance and loss is calculated from the resonant properties and compared with the simultaneously measured 1 MHz capacitance and dissipation. Two-tone intermodulation distortion products were measured and the third-order intercept is referenced to the microwave voltage across the capacitors. Commercially available semiconductor varactors were tested in a similar manner. The tuning quality (the ratio of the relative capacitance tuning to dissipation), frequency dispersion, and power handling of these capacitors are compared. Although there appears to be no intrinsic power handling advantage of the paraelectrics over the semiconductor varactors, the paraelectric varactors can offer better tuning quality.
Dielectric and Structural Properties of (100) KTa1−xNbxO3 Films Grown on MgO, LaAIO3 and SrTiO3 Substrates by Pulsed Laser Deposition
Authors: Chang Wontae , Carter Adriaan C. , Horwitz James S. , Kirchoefer Steven W. , Pond Jeffrey M. , Grabowski Kenneth S. , Chrisey Douglas B.
Published: April 2011

KTa1−xNbxO3 (KTN) thin films (-6000 Å) were grown on (100) MgO, (100) LaAlO3 (LAO), and (100) SrTiO3(STO) substrates by pulsed laser deposition (PLD). Deposited films were smooth, single phase and exclusively (100) oriented. KTN films deposited on MgO and LAO substrates were easily cracked after deposition or post deposition heat treatment. The film deformation appeared to be caused by strain due to the lattice mismatch between the film and the substrate. A thin buffer layer of ∼100 Å was used to eliminate the cracking problem. The high volatility of K at the film deposition temperature required excess K to be added to the ablation target. Sintering of the target and post-deposition annealing of the films were done in a sealed Pt coated stainless steel container. Rutherford backscattering showed the films to have a 1 to 1 atomic ratio of K to Ta + Nb. On top of the KTN films, Ag interdigitated capacitors were deposited. Room temperature measurements of capacitance and dielectric loss as a function of bias electric field (0 -80 kV/cm) at 1 to 20 GHz were made. Capacitance and dielectric loss measurements were made as a function of temperature and bias electric field at one MHz and as a function of temperature and frequency at 0V DC bias. The results show the strong potential of KTN for use in frequency agile microwave electronics.
Epitaxial lift-off of strontium titanate thin films and the temperature dependence of the low frequency dielectric properties of the films
Authors: Dalberth M. J. , Price J. C. , Rogers C. T.
Published: April 2011

Using pulsed laser ablation, we have grown epitaxial bilayers of strontium titanate (STO) and yttrium barium copper oxide (YBCO) on lanthanum aluminate (LAO) and neodymium gallate (NGO) substrates. Using a selective acid etch, we have removed the YBCO from the middle of the bilayer and lifted off the strontium titanate films from their parent substrates. Using coplanar interdigital capacitors patterned on the films' surface, we have measured the dielectric constant and loss as a function of frequency and temperature and have resolved frequency dependent loss peaks which indicate thermally activated behavior. Also, by applying a dc bias to the capacitor, we have seen tuning of the lifted off films' dielectric constants that compares favorably to films attached to substrates.
The Growth of Nonlinear Optical Thin Films of KTa1−xNbxO3 on GaAs by Pulsed Laser Deposition for Integrated Optics
Authors: Knauss L. A. , Harshavardhan K. S. , Zhang H. Y. , He X. H. , Shih Y. H. , Grabowski K. S. , Knies D. L.
Published: April 2011

Nonlinear optical films on GaAs and other III-V (AlGaAs, InGaAs) semiconducting substrates have many potential applications in integrated optics. Until now, the growth of device quality films on GaAs was a major technological challenge. Using Pulsed Laser Deposition (PLD) epitaxial films of prototypical nonlinear KTa0.52Nb0.48O3 (KTN) were successfully deposited on single crystalline GaAs substrates for the first time. In order to alleviate chemical and structural incompatibilities between the GaAs substrate and KTN film at the growth temperature (∼750°C), a novel buffer layer scheme consisting of epitaxial MgO and SrTiO3 buffer layers and a Si3Ni4 encapsulation of the substrate was successfully developed. To obtain films with the required stoichiometry, a segmented target geometry was used consisting of KTN and KNO3 targets. The high crystalline quality of KTN films on GaAs was established by detailed 4-circle x-ray diffraction studies. Rutherford Backscattering studies confirmed the composition of the films. Optical measurements have been carried out on epitaxial KTN films on GaAs. Using an Ar+ laser (457.9 nm) operating in the TEM00 mode, we have observed sharp and distinguishable TE and TM propagating modes in KTN films. The refractive index (n0) of the film at 488 nm is 2.275 which is close to the bulk value of 2.35.
Process Optimization for Piezoelectric Films and Coatings
Authors: Sayer M. , Zou L. , Leclerc B. , Lukacs M. , Olding T. , Schloss J. H.
Published: April 2011

The dielectric and piezoelectric response of sol gel based films and composite coatings is affected by the choice of process, gel composition, thermal cycle, processing atmosphere and poling conditions. Important general factors for thin films are the crystallization kinetics and the effects of residual carbon, while a new dielectric technique allows poling methods to be evaluated.
Antiferroelectric Thin Films for Decoupling Capacitor and Microactuator Applications
Authors: Xu Baomin , Pai Neelesh G. , Moses Paul , Eric Cross L.
Published: April 2011

Lanthanum-doped or niobium-doped lead zirconate titanate stannate antiferroelectric thin films with the thickness of about 0.4 μm have been prepared from acetic acid-based or 2-methoxyethanol-based sol-gel method. All the films have the maximum polarization larger than 30 μC/cm2 and show zero remanent polarization. By choosing appropriate compositions, we can make the films have “square” hysteresis loops with very sharp phase transition or “slanted” hysteresis loops with very small hysteresis. The properties that are important for decoupling capacitor and microactuator applications are characterized. For decoupling capacitor applications, films having square hysteresis loops with energy storage density of up to 7 J/cm3 can be made, which release more than half of their stored charge in 10 ns with a maximum current density of more than 9400 A/cm2. For microactuator applications, the films can either have a strain level of 0.32% with very small hysteresis or have a strain level of 0.42% with moderate hysteresis.
Direct Wafer Bonding and Layer Transfer: An Innovative way for the Integration of Ferroelectric Oxides into Silicon Technology
Authors: Alexe M. , Senz St. , Pignolet A. , Scott J. F. , Hesse D. , Gösele U.
Published: April 2011

An innovative fabrication process of ferroelectric-semiconductor heterostructures based on direct wafer bonding has been demonstrated. Ferroelectric thin films of Bi4Ti3O12 (BiT) and Pb(Zr,Ti)O3 (PZT) were deposited on 3” Si wafers using chemical solution deposition (CSD) and subsequently crystallized by conventional and rapid thermal annealing. The films were then polished in order to reach a roughness and waviness suitable for bonding. They were then directly bonded to silicon wafers in a micro-cleanroom and annealed in air at temperatures ranging from 200°C to 500°C. Bonding energies up to 1.5 J/m2 have been achieved which is almost high enough to consider the two bonded wafers as a single body. Metal-Ferroelectric-Silicon (MFS) structures containing the ferroelectric-Si bonded interface were accomplished by polishing down and etching the handling wafer. The MFS structures were electrically characterized by capacitance-voltage (C-V) and charge-voltage (Q-V) measurements.
Nanoscale Investigation of Polarization Retention Loss in Ferroelectric Thin Films VIA Scanning Force Microscopy
Authors: Gruverman A. , Prakash S. A. , Aggarwal S. , Ramesh R. , Auciello O. , Tokumoto H.
Published: April 2011

Scanning force microscopy (SFM) was applied to direct nanoscale investigation of the mechanism of retention loss in ferroelectric thin films. Experiments were conducted by performing local polarization reversal within an individual grain with subsequent imaging of a resulting domain structure at various time intervals. A conductive SFM tip was used for domain switching and imaging in the SFM piezoresponse mode.
Synthesis and photoresponse of rare earth doped phosphosilicates
Authors: Cao Z. , Lee B. I. , Samuels W. D. , Exarhos G. J. , Wang L.
Published: April 2011

Phosphate ceramics doped with Sm3+ and Tb3+ ions were synthesized through sol-gel process. Thin films of Tb3+ doped phosphosilicates were fabricated by spin coating of the phosphosilicate sols on SiOx/indium-tin-oxide/glass substrates. The gels synthesized by reaction of P2O5 with tetraethoxy silane (TEOS) were fired in air at a temperature range of 200°C – 900°C. The crystal structure was examined by x-ray diffractometry. Si5O(PO4)6 was the only crystalline phase. The fluorescence spectra of Sm3+ as a function of firing temperature, composition and structure of the matrices were investigated. The intensity of Sm3+ emission increased with increasing firing temperatures and greater proportion of phosphorus. The photocurrent of the films at 355 nm laser excitation was observed. The photoresponse as a function of laser energy was linear and showed no sign of saturation. The films exhibited stable photoresponse under a high number of laser shots.
Formation of Transparent SiO2 Thin Film at Room Temperature with Excimer Lamp Irradiation
Authors: Okamoto T. , Iizuka H. , Ito S. , Murahara M.
Published: April 2011

A transparent SiO2 thin film was grown with Xe2* excimer lamp and NF3, O2 mixed gases at room temperature. Unlike the conventional methods such as atomic layer epitaxy (ALE) at low temperature, this method requires only a few minutes for deposition without changing material gases. A Si substrate was placed in a reaction chamber, which was filled with NF3 and O2 gases. The gases were exposed to the Xe2* excimer lamp light, and SiF4 and NO2 were produced by photochemical reaction. The SiF4 was adsorbed on the substrate; which reacted with NO2 in gas ambient and was oxidized to form SiO2. The molecular layer was produced per reaction, and by voluntarily repeated reaction, the transparent SiO2 thin film was grown. As a result, the SiO2 film thickness of about 2200 Å was achieved for 15 minutes at room temperature. By annealing the formed SiO2 film, the surface current density of the formed SiO2 decreased; the higher the annealing temperature became, the more the surface density decreased.
Advanced Metal/Ceramic Catalysts for Hydrogen Generation by Steam Reforming of Hydrocarbons
Authors: Tikhov S. F. , Sadykov V. A. , Salanov A. N. , Potapov Yu. A. , Litvak G. S. , Tsybulya S. V. , Pavlova S. N.
Published: April 2011

The main features of porous metal/ceramic catalysts for hydrocarbons steam reforming their formation via hydrothermal treatment of the powdered aluminum and lanthanum nickelate mixture in the confined space are elucidated. For catalysts obtained via this route, their polymodal pore structure was found to approach the optimum level. The phase composition of the active component precursor was shown to have a great impact on the specific catalytic activity of catalysts.
Reversible Hydrogen Uptake in Carbon-Based Materials
Authors: Brown S. D. M. , Dresselhaus G. , Dresselhaus M. S.
Published: April 2011

Several approaches for achieving reversible hydrogen uptake by carbon are considered, including intercalation, adsorption by a graphite surface, hydrogenation of fullerenes, and the filling of carbon nanotubes. Most scenarios suggest that it is difficult to achieve an atomic uptake [H/C] ratio exceeding unity. Evidence for H2 uptake by various carbon materials is reviewed.
Mixed Metal Phospho-Sulfates for Acid Catalysis
Authors: Thoma S. G. , Jackson N. B. , Nenoff T. M. , Maxwell R. S.
Published: April 2011

Mixed Metal Phospho-Sulfates were prepared and evaluated for use as acid catalysts via 2-methyl-2-pentene isomerization and o-xylene isomerization. Particular members of this class of materials exhibit greater levels of activity than sulfated zirconia as well as lower rates and magnitudes of deactivation. 31P MAS NMR has been used to examine the role of phosphorous in contributing to the activity and deactivation behavior of these materials, while powder X-ray diffraction, BET surface area, IR, and elemental analysis were used to characterize the bulk catalysts.
A Novel TiO2 Film Catalyst — Preparation, Properties and Research on its Photocatalytic Oxidized Activity
Authors: Cao Y. A. , Zhang X. T. , CHONG L. Q. , WANG D. Y. , XIE T. F. , HUANG Y. , CUI Z. F. , SHI W. G. , LIU X. J. , WU Z. Y. , BAI Y. B. , LI T. J. , WU Y.
Published: April 2011

A new kind of TiO2 film catalyst was prepared by the Plasma-enhanced chemical vapor deposition (PECVD) method. The surface photovoltaic spectroscopy (SPS) results showed that its photoresponse was extended into the visible region. Photooxidation experiments showed that this kind of TiO2 film had high photocatalytic activity on degradation of phenol in aqueous solution. The influence of the thickness of TiO2 film on its photocatalytic activity was also discussed.
Theory of Electron Field Emission From Diamond And Diamond-Ldxe Carbon
Authors: Robertson J
Published: April 2011

It is shown that the facile electron field emission from diamond and diamond-like carbon occurs because surface groups such as C-H can produce large changes in electron affinity, so that electric fields from the anode can be focused towards unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer. The resulting downwards band bending creates very large fields which cause Fowler-Nordheim emission, while not exceeding the material's breakdown field, which is the highest for any solid.
The Interaction of Carbon with the Diamond Surface: A Photoelectron Spectroscopy Study
Authors: Reinke P. , Wrase T. , Müller K. , Oelhafen P. , Locher R.
Published: April 2011

The modification of the diamond surface through adsorbants offers the opportunity to adjust the electronic and electron emission properties of the surface. In the study presented here, we deposited between 0.1 and 100 monolayers of carbon from an electron beam evaporation source on polycrystalline diamond films. Photoelectron spectroscopy in the ultraviolet and X-ray regime was employed to characterize the surface. Observations on a (100) polycrystalline diamond film show, that the surface is first depleted of hydrogen and subsequent growth of an amorphous carbon film (a-C) occurs on the reconstructed surface. The deposition of these ultrathin carbon films allows the controlled introduction of sp2carbon and p-π states onto the diamond surface. The field emission current increases considerably with the amount of sp2-carbon accumulated at the diamond surface. The current-voltage characteristics only partially follow the Fowler-Nordheim equation, and the results obtained for different films are described and possible emission mechanism discussed.
Evaluation of Free Energy Differences Between Crystalline Phases Using the Lattice-Switch Monte Carlo Method
Authors: Ackland G. J. , Wilding N. B. , Bruce A. D.
Published: April 2011

A new method [1] of calculating the free energy difference between two crystalline structures is presented. The method involves a single simulation which repeatedly transforms the system between the two crystal phases. Since the configurations of both structures are sampled within a single Monte Carlo process, the difference between their free energies can be evaluated directly from the ratio of the measured probabilities of each. Compared with traditional techniques, the method is most advantageous when applied to highly anharmonic systems. To illustrate the method, an application to the free energy difference between the fee and hep structures of hard spheres is described.
Novel Structure of MgSe in the Multimegabar Regime: Positional Parameter Determination
Authors: Ruoff Arthur L. , Li Ting , Narayana Chandrabhas , Luo Huan , Greene Raymond G.
Published: April 2011

The structural transformations in the II-VI compound MgSe have been studied under pressure using energy dispersive x-ray diffraction. MgSe transforms ‘continuously’ from the rocksalt (Bl) structure to a FeSi (B28) or Au-Be structure beginning at 99 ± 8 GPa. At 202 GPa, MgSe is approaching 7-fold coordination withu= 0.0828 andw= 0.4173. The method for intensity calculation of the diffraction peaks is presented. Using the Birch equation, the equation of state to 146 GPa was determined with Bo= 62.8 + 1.6 GPa and Bo′ = 4.1.
Pressure as a Probe of the Glassy State of Ferroelectrics with Random Site Disorder
Authors: Samara G. A. , Hansen L. V.
Published: April 2011

Results on lanthanum-modified lead zirconate-titanates (PLZTs) have revealed a pressure-induced crossover from a normal ferroelectric to a relaxor state and the continuous evolution of the dynamics and energetics of the relaxation process. This crossover appears to be a general feature of soft mode ferroelectrics with random site dipolar impurities or polar nanodomains and results from a large decrease in the correlation radius among polar nanodomains - a unique property of soft mode ferroelectrics.
Surface and bulk properties of boride/nitride nanoscale films
Authors: Adrievski R. A.
Published: April 2011

Nanoscale TiB2/TiN films have been prepared by d.c. and r.f. magnetron non-reactive sputtering and examined by TEM, SAED, SEM, AES, XPS, XRD, AFM as well as nanoindentation. Attention has been focused on both bulk and surface physical-mechanical properties. The effect of the latter on the nanoindentaion test results seems to be very important. Two types of film fracture under a Vickers indentor connected with homogeneous and inhomogeneous deformation have been described.
Drifts surface characterization of Zincblende nanostructured GaN
Authors: Gonsalves Kenneth E. , Carlson Greg , Baraton Marie-Isabelle
Published: April 2011

The use of GaN/polymer nanocomposites in optoelectronics requires a perfect control of the GaN dispersion in the polymer matrix. This cannot be achieved without a good knowledge of the first atomic layer of the GaN nanoparticles. This paper reports the characterization of the surface chemical species of a GaN nanosized powder by diffuse reflectance infrared Fourier transform spectrometry.
Block Copolymer Monolayers at Surfaces
Authors: Saunders R. S. , Kent M. S. , Small J. H.
Published: April 2011

Monolayers on surfaces have become a topic of considerable interest over the last few years. This has arisen from the need to functionalize a surface so that its properties are different than the properties of the bulk material. This research has involved functionalizing copper surfaces to enhance adhesion to epoxy. We have accomplished this using block copolymers made by Ring-Opening Metathesis Polymerization (ROMP). In this paper we discuss the synthesis and characterization of these block copolymers and their segregated monolayer conformation at copper surfaces, including NMR, GPC, SANS, neutron reflectivity, and TOF-SIMS. We also discuss a comparison of block copolymers to SAMS for surface functionalization.

Monolayers on surfaces have become a topic of considerable interest over the last few years. This has arisen from the need to functionalize a surface so that its properties are different than the properties of the bulk material. This research has involved functionalizing copper surfaces to enhance adhesion to epoxy. We have accomplished this using block copolymers made by Ring-Opening Metathesis Polymerization (ROMP). In this paper we discuss the synthesis and characterization of these block copolymers and their segregated monolayer conformation at copper surfaces, including NMR, GPC, SANS, neutron reflectivity, and TOF-SIMS. We also discuss a comparison of block copolymers to SAMS for surface functionalization.
Microstructure and properties of oxide ceramic-based nanocomposites with transition metal nanoparticles
Authors: Sekino T. , Etoh S. , Choa Y.-H. , Niihara K.
Published: April 2011

Transition metal particles dispersed oxide ceramic nanocomposites A12O3/Co and ZrO2/Ni, in which metal content is less than 20 vol%, have been fabricated by the reduction and sintering of composite powders. These powder mixtures were prepared by solution chemical processes to obtain suitable structure for ceramic/metal nanocomposites. Nickel or cobalt nitrate, as a source of metal dispersion, was dissolved into alcohol and mixed with alumina or zirconia powder. These powders were reduced by hydrogen and successively hot press sintered. Nanometer-sized Co or Ni particles were mainly dispersed at the matrix grainboundaries. Fracture strength was improved by dispersing metal particles due to microstructural refinement, whereas toughness was increased by incorporating large metals. Ferromagnetic responses with enhanced coercive force were also observed for these composites.
Synthesis of Nanoscaled Powders by Laser-Evaporation of Materials
Authors: Riehemann W.
Published: April 2011

Ultra fine powders with particle diameters less than 100 nm are becoming increasingly important for various electronic, magnetic and chemical applications as well as in nanostructured materials with extremely fine grained components. Nowadays there are a lot of methods available to synthesize nanoscaled powders. One of the most versatile production methods delivering clean particle surfaces is laser evaporation. Interaction of high intensity laser beams with materials leads to evaporation and subsequent condensation of very small mostly spherical particles with diameters in the order of 10 nm. This means specific surfaces of the powders in the order of 100 m2/g. Depending on the lasers intensity, the surrounding gas, its pressure, and the evaporated material the particles have mean diameters ranging from 4 to 20 nm. Their distribution is generally lognormal with a geometrical standard deviation in the narrow range between 1.5 and 1.7. These properties of the powders can be explained by their originating mechanism, nucleation and particle growth in the surrounding gas. With this method nanosized powders of various materials can be produced like pure metals, alloys, metal oxides, other ceramics and new phases which are probably stabilized by the small particle size. Using a 1 kW - Nd:YAG - laser powder production rates of up to 100 g/h can be achieved for alumina. Contrary to other synthesis methods e.g. the sol-gel method the produced nanoparticles are in particular free of solvents or other residuals. This makes laser synthesised powders extremely usefiil for catalytic or gas sensor applications where defined surface qualities are necessary.
Preparation and properties of phenytoin silica complex nanoparticles
Authors: Goto H. , Isobe T. , Senna M.
Published: April 2011

A sparingly soluble model drug, phenytoin (5,5-diphenyl-hydantoin, denoted as PT), was added during hydrolysis and polycondensation of tetra orthoethyl silicate (TEOS). The average size of the composite primary particles after in situ recrystallization of PT and gelation of silica was 2–3nm. The extent of hydrogen bond (HB) in PT was reduced after the complex formation (CF), while many PT molecules were attached by HB on the surface of silica gel. The apparent solubility to ethanol decreased to 29%∼18% by CF. The firstorder rate constant of dissolution of PT into H20 increased by CF up to 40 times. Addition of acrylamide also enhanced the dissolution rate. Mechanisms of faster dissolution were discussed in terms of the hydrogen bond reformation and microstructure.
Nanoparticulate film precursors to cis solar cells: Spray deposition of Cu-In-Se colloids
Authors: Schulz D. L. , Curtis C. J. , Flitton R. A. , Ginley D. S.
Published: April 2011

The use of nanoparticle colloids for spray deposition of Cu-In-Se precursor films and subsequent thermal treatment to form CuInSe2 (CIS) films has been investigated. In the present study, the metathesis reaction between Na2Se in methanol and metal salts (i.e., Cu(BF4)2 and/or InI3) in pyridine produced CuSe, In2Se3, and CuInSe2.5 nanoparticle colloids. Purified colloid was sprayed onto heated molybdenum-coated sodalime glass substrates to form CuInSe2.5/Mo and In2Se3/CuSe/Mo precursor films. These precursor films were subjected to various thermal treatments in an effort to produce large-grained CIS films from the nano-sized precursors. The annealed CIS films were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD). Results of this continuing effort will be discussed.
Control of particle adhesion to surfaces by depositing nanometric interfacial layers
Authors: Ata Ali , Fitz-Gerald J. , Singh R. K.
Published: April 2011

The influence of nano-thick hydrophilic or hydrophobic films on adhesion properties of particles to surfaces has been investigated. Al2O3 and Ag layers were deposited on Ag and Al2O3 core particles, respectively by a modification of pulsed laser deposition technique. The as-received and surface-modified particles were further coated by a secondary process with submicron Al2O3 particles. We observe that deposition of hydrophobic or hydrophilic surfaces affects the surface coverage of secondary particles on core particles and hence the adhesion characteristics.
Optical properties of nonspherical silver nanoparticles embedded in a plasma polymer thin film matrix
Authors: Heilmann A. , Quinten M. , Kiesow A.
Published: April 2011

Silver nanoparticles which are embedded in a plasma polymer matrix were obtained by transmission electron microscopy. Their sizes and shapes were analyzed with optical image processing. As most of the particles appeared as elongated rotational ellipsoids, the major and minor half axes were determined for each particle. The model of Gans in the Rayleigh approximation was used to calculate the extinction spectra for each investigated particle using the data from the image processing. Various spectra for 1049 silver particles were added to get a total extinction spectrum which was in good agreement with the experimental spectrum.
Optical properties of gold-containing Poly(acrylic acid) composites
Authors: Scholz S. M. , Carrot G. , Hilborn J. , Dutta J. , Valmalette J.-C. , Hofmann H. , Luciani A.
Published: April 2011

There is strong interest in the research & development of the particle/polymer composite technology for functional applications. Current activities are directed towards polymer assisted synthesis of ultrafine metal or semiconductor particles in solution, with an ultimate goal to arrange the particles in a matrix in well-controlled fashion, for possible electro-optical applications. In the present work the optical properties of poly(acrylic acid) polymers containing gold chloride have been investigated. This material system permits synthesis of gold nanoparticles by the reduction of gold chloride. The polyelectrolyte initially forming upon mixture of the reagents shows a gelating behavior. In-situ reduction into gold clusters can be achieved by several ways. Rheological properties, optical absorption/extinction spectra as well as photoluminescence and photoluminescence excitation spectra will be presented and discussed. Different possible combinations of gold ligands and co-ordinations states will be considered in the discussion. Gold may be present in the form of complexes, to the polyelectrolytes, or in form of nanoparticles or larger aggregates depending on the relative concentrations of the reagents and polymer molecular weight.
In-Situ DLTs Measurement of Metastable Coupling between Proton-Induced Defects and Impurities in n-Si
Authors: Kono K. , Kishimoto N. , Amekura H.
Published: April 2011

Deep centers related to proton-induced defects and impurities in n-Si were investigated using an in-situ DLTS system. The measurement system was installed in the beamline of NRIM cyclotron. Floating zone (FZ) or Czochralski (CZ) Si was irradiated at a flux of about 30 nA/cm2. The total dose was varied between 1.0 ∼ 7.2 × 1013 ions/cm2. Samples were irradiated at 200 K or 300 K. Their defect concentrations were determined by in-situ DLTS. Quantitative relationship between oxygen and phosphorus concentration and defect creation rates were presented. Isothermal annealing at 250 K was conducted for a CZ-Si sample and the resuflt indicated the meta-stable nature of the carbon defect complex.
Metastable Amorphous SiO2 created by Ion Bombardment
Authors: Awazu Koichi , Roorda Sjoerd , Brebner John L.
Published: April 2011

Structural changes in thin amorphous SiO2 (a-SiO2) films induced by ion bombardment were examined with FT-IR and ESR techniques. 10MeV H+, 15MeV He+, 2MeV Li+, 4MeV C+ and 30MeV Si6+ ions, which traverse the 200nm thick of SiO2 layer without chemical reaction with SiO2, were used as ion beams with dosage of 1012−1016cm−2. A decrease in the frequency of one peak in the infrared absorption spectrum from 1078cm−1 to 1041cm−1 and an increase of a second peak from 805cm−1 to 830cm−1 were simultaneously observed with cumulative ion dose. The concentration of E' centers has a maximum as a function of dosage in the region of 1–5×1019cm−3. We propose that a reduction of the Si-O-Si bond angle followed by displacement of oxygen is induced with ion bombardment.
Change in yhe Optical Properties of Sapphire Induced by Ion Implantation
Authors: Ila D. , Williams E. K. , Sarkisov S. , Poker D. B. , Hensley D. K.
Published: April 2011

We have studied the formation of nano-crystals, after implantation of 2.0 MeV gold, 1.5 MeV silver, 160 keV copper and 160 keV tin into single crystal of A12O3. We also studied the change in the linear optical properties of the implanted Al2O3 before and after subsequent annealing by measuring the increase in resonance optical absorption. Applying Doyle's theory and the results obtained from Rutherford backscattering spectrometry (RBS) as well as the full width half maximum of the absorption band from Optical Absorption Photospectrometry (OAP), we measured the average size of the metallic clusters for each sample after heat treatment. The formation and crystallinity of the nanoclusters were also confirmed using transmission electron microscopy (TEM) technique.
Ion Beam Synthesis Of Cds, ZnS, And PbS Compound Semiconductor Nanocrystals
Authors: White C. W. , Budai J. D. , Meldrum A. L. , Withrow S. P. , Zuhr R. A. , Sonder E. , Purezky A. , Geohegan D. B. , Zhu J. G. , Henderson D. O.
Published: April 2011

Sequential ion implantation followed by thermal annealing has been used to form encapsulated CdS, ZnS, and PbS nanocrystals in SiO2 and Al2O3 matrices. In SiO2, nanoparticles are nearly spherical and randomly oriented, and ZnS and PbS nanocrystals exhibit bimodal size distributions. In Al2O3, nanoparticles are facetted and oriented with respect to the matrix. Initial photoluminescence (PL) results are presented.
Formation of Pb Inclusions in Si by Ion Implantation
Authors: Touboltsev V. S. , Johnson E. , Dahmen U. , Johansen A. , Sarholt L. , Xiao S. Q.
Published: April 2011

Abstracr

Si<110> single crystals were implanted at a temperature of 835 K with 150 keV Pb+ ions to a fluence of 1·1020 m−2 corresponding to an average concentration of 2–3 at%. The implanted samples have been studied by Rutherford Backscattering (RBS)/channeling and transmission electron microscopy (TEM) techniques. In as-implanted samples the main fraction of implanted Pb was located on substitutional sites in the Si matrix thus providing a highly supersaturated solution of Pb in Si. Spontaneous precipitation of Pb, giving rise to formation of nanosized Pb inclusions, was found to take place only in the peak region of the implantation. TEM analysis showed that the Pb precipitates had sizes from about 2 to 20 nm and that they grew in parallel cube orientation relationship with the host matrix. The shape of the inclusions was found to be approximately cuboctahedral with poorly developed {111} and {100} facets.

In-situ RBS/channeling heating/cooling experiments on both as-implanted samples and samples previously furnace-annealed at 1175 K showed a distinct melting/solidification hysteresis of the Pb inclusions around the bulk melting point for Pb at 600 K. These results were verified by in-situ TEM heating/cooling experiments on as-implanted samples.