bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nickel-Related Optical Centers in Hpht Treated Synthetic Diamonds: Photoluminescence Study
Authors: Kupriyanov I.N. , Gusev V.A. , Pal'yanov Yu.N. , Borzdov Yu.M. 
Published: April 2011

ABSTRACTThe results of a photoluminescence (PL) study of synthetic diamonds annealed over the temperature range 1500-2500°C are presented. For nickel- and nitrogen-containing diamonds a number of new, previously undocumented PL systems with zero-phonon lines (ZPLs) at 598.5, 622.6, 638.9, 752.1 and 877.2 nm has been found. Photoluminescence excitation (PLE) spectra for PL systems with ZPLs at 727.1 and 746.6 nm have been measured for the first time. Preliminary results on annealing behavior of the PL centers have been obtained. Of all the PL systems observed only that ones with ZPLs at 752.1 and 793.0 nm together with the S2 and S3 optical centers are present in diamonds annealed at temperatures higher than 2200°C.
First-Principles Calculation of Optical Spectra for Transition-Metal Impurities Doped in Zno and Zns
Authors: Ogasawara K. , Ishih T. , Oba F. , Tanaka I. , Adachi H. 
Published: April 2011

ABSTRACTThe multiplet structures of Co2+ doped in ZnO, Co2+ doped in ZnS and Ni2+ doped in ZnS are calculated from first principles using the recently developed discrete variational-multielectron (DV-ME) method, in which the matrix elements of electron-electron repulsion are calculated numerically using the molecular orbitals obtained by cluster calculations. The transition probabilities between the multiplet states are also calculated from first principles using the many-electron wave functions obtained by the DV-ME calculations. The optical spectra of these materials are well reproduced, indicating that the effects of covalency and configuration interactions are properly taken into account in the present calculations.
A Sims Study of Electroluminescent Phosphors: SrS:Cu
Authors: Zhang Lily H. , Wang Larry , Tong Wusheng , Xin YongBao 
Published: April 2011

ABSTRACTThis study has used secondary ion mass spectrometry (SIMS) as a technique for thin film EL material characterization. It has shown that the Cu dopant concentration in the SrS films directly correlates with the luminescent brightness of the EL devices. A series of SrS:Cu,Y were grown using MBE to study the Y co-doping effects. It has been found that Y peak concentration and areal density in the SrS increased as the Y evaporation cell temperature was increased. The maximum PL intensity was found in the sample grown in the middle of the Y cell temperature range used. The Y co-doping has shown to reduce the thermal quenching effects in SrS EL devices. Therefore, in this series of samples, a good correlation has been found between Y and Cu concentration and the EL device performance characteristics.
Self-Assembly Processes for Organic Led Transport Layers and Electrode Passivation
Authors: Malinsky J.E. , Li W. , Wang Q. , Cui J. , Chou H. , Marks T.J. , Jabbour G.E. , Shaheen S.E. , Anderson J.D. , Lee P. , Richter A.G. , Kippelen B. , Dutta P. , Peyghambarian N. , Armstrong N. 
Published: April 2011

ABSTRACTThis contribution describes the use of self-limiting siloxane chemisoroption processes to self-assemble building blocks for the modification of vacuum-deposited organic LED (OLED) devices. One approach consists of the use of self-assembling OLED hole transport materials for application in hybrid self-assembled + vapor deposited two-layer devices. Another approach involves the application of self-limiting, chemisorptive self-assembly techniques to introduce thin dielectric films between the anode and hole transport layer of a vapor deposited two-layer OLED device.
Determination of the Coefficient of Piezoresistivity in Aluminum Alloy Interconnect Structures
Authors: Reilly Christopher J. , E John , Jr Sanchez 
Published: April 2011

AbstractThe resistance of Al thin film metallization interconnects has been measured during temperature cycling where thermal expansion mismatch between the Al and the substrate and passivation is used to induce interconnect strain. Both passivated and unpassivated interconnects were thermally cycled between 80K and 373K. The coefficient of piezoresistivity, defined as dp/dE, where ρ= resistivity and εv = volumetric strain, is measured to be 2.0 10−5Ω-cm in tension, consistent with previous results determined in bulk Al under hydrostatic pressure. We describe a model which incorporates the thermal, geometrical, and piezoresistance effects on the measured interconnect resistance during temperature changes. Thermal expansion mismatch strains and the degree of interconnect constraint by the rigid surrounding materials, which vary with interconnect aspect ratio, are considered. The application of piezoresistance analysis to measurement of local stresses and stress relaxation in advanced interconnects will be described.
Sidewall-Fence-Free Pt Etching with an Ar/O2 Mixed Gas Plasma
Authors: Chiang M.-C. , Pan F.-M. , Wei T.-C. , Chien H.-C. , Liou J.-S. , Chiu H.-K. 
Published: April 2011

AbstractPlatinum has been successfully patterned with a TiN mask in an Ar/O2 plasma.No fence residue was observed on the etched Pt pattern if the thickness of the TiN mask was less than 300 nm. During the etching process, titanium dioxide and platinum oxides were formed and redeposited on the mask and the Pt structure in the Ar/O2 plasma according to Auger and XPS analyses. The etch rates of Pt and TiN films decreased with increasing oxygen concentration in the Ar/O2 gas mixture. The addition of O2 inthe gas mixture could improve the sidewall slope of the etched Pt structure. This was ascribed to redeposited platinum oxides and TiO2 on the sidewall, which makes the sidewall more resistant to ion etching at a higher concentration of oxygen.
PECVD of Low Dielectric Constant Fluorine-Doped SiO2 Using TICS/O2/TFAA with In-Situ Annealing
Authors: Idris I. , Sugrura O. 
Published: April 2011

AbstractA fluorine-doped silicon dioxide (SiO2:F) film with dielectric constant as low as 3.0 was deposited by introducing trifluoroacetic anhydride ((CF3CO) 2O TFAA) into our hydrogen-free SiO2 PECVD system using tetraisocyanatesilane (Si(NCO)4 TICS) and O2. The film was deposited at 100°C and 0.5 Torr. It was annealed by in-situ, 0.2 Torr O2 plasma treatment at 400°C for 1 hour, as well as post-metallization annealing in N2 ambient at 400°C for 1 hour. The refractive index and the ratio of infrared absorbance of Si-F/Si-O-Si peak intensity were 1.37 and 11.7%, respectively. No peak related to water absorption was clearly observed in its infrared spectrum even after contact-holes opened and dipped into boiling water for 2 hours.
Reliability of Electrodeposited Copper and Ecrcvd Siof Films for Multilevel Metallization
Authors: Lee Seoghyeong , Kim Yong-An , Lee Kyoung-Woo , Sohn Seil , Kim Young-Il , Yang Sung-Hoon , Oh Kyunghui , Park Jong-Wan 
Published: April 2011

AbstractThe effect of a post plasma treatment on the dielectric properties and reliability of fluorine doped silicon oxide (SiOF) films deposited by electron cyclotron resonance chemical vapor deposition (ECRCVD) was studied. Also, the thermal stability of an electrodeposited Cu / sputtered Ta interconnect system with SiOF intermetal dielectrics was examined by annealing in a vacuum furnace. The stability of the dielectric constant of SiOF films was improved by O2 post plasma treatment. Surface modification by the plasma treatment was effective in prevention of water absorption. The Cu/Ta/SiOF/Si system was thermally stable at least up to 500°C for 3h. For the Cu/Ta/SiOF/Si multilayer structure, the plasma treatment seemed to play a big role in suppressing the interdiffusion between SiOF and metal interconnects. By C-V measurement, the electrical stability of the Cu/Ta/SiOF/Si multilayer structure was found to be stable up to 500°C for 2 h.
Mask-Induced Strain in Gaas Layers Grown by Liquid Phase Epitaxial Lateral Overgrowth
Authors: Zytkiewicz Z.R. , Domagala J. , Dobosz D. 
Published: April 2011

ABSTRACTX-ray diffraction has been used to study the mask-induced strain in GaAs layers grown by the liquid phase epitaxial lateral overgrowth (ELO) on (100) GaAs substrates. SiO2 mask has been investigated to produce seeding areas for the ELO growth. It has been found that SiO2 attracts the ELO layers, which leads to their pronounced bending towards the oxide film and to the appearance of vertical strain in laterally grown parts of ELO. When SiO2 is removed by selective etching this strain disappears. We show evidence that the bending of ELO layers is reduced when the density of substrate dislocations is increased. This is explained as being due to enhancement of the initial vertical growth rate by dislocations supplying steps on the upper surface of ELO.
Epitaxial Growth of Atomically Flat Spin Dependent Tunneling Junctions
Authors: Li Y. , Wang S. X. , Mancoff F. B. , Clemens B. M. 
Published: April 2011

ABSTRACTSpin dependent tunneling junctions with epitaxially grown underlayers have been investigated to examine the possibility of achieving very flat and uniform barrier layers. Pt/Ni80Fe20 /Fe50Mn50/Ni80Fe20layers were deposited on sapphire (0001) substrates at different temperatures and monitored by in-situ reflection high energy electron diffraction (RHEED). The surface morphology has been found to depend strongly on the growth temperature. X-ray diffraction and magnetic hysteresis loop measurements were also performed to characterize the film structures
A Formation of SiO2/4H-SiC Interface by Oxidizing Deposited Poly-Si and High Temperature Hydrogen Annealing
Authors: Fukuda K. , Sakamoto K. , Nagai K. , Sekigawa T. , Yoshida S. , Arai K. 
Published: April 2011

ABSTRACTA formation of SiO2/4H-SiC interfaces by oxidizing deposited poly-Si on a 4H-SiC substrate and high temperature hydrogen annealing at low pressure ( 8.5×102 Pa ) has been investigated. The oxidation rate of deposited poly-Si was approximately 100 times faster than that of a SiC. Hydrogen annealing more effectively reduced the flat band voltage shift ( ΔVfb ) of the 4H-SiC MOS structure than argon and vacuum annealing. Moreover, the good SiO2/4H-SiC interface was formed because ΔVfb decreased as the oxidation temperature increased.
Polytype Stability and Defect Reduction in 4H-SiC Crystals Grown via Sublimation Technique
Authors: Yakimova R. , Iakimov T. , Syvdijarvi M. , Jacobsson H. , Råback P. , Vehanen A. , Janzén E. 
Published: April 2011

ABSTRACTReproducible growth of 4H-SiC with good crystalline quality has been obtained in a temperature interval around 2350°C and on 4H-SiC C-face seeds. It has been observed that morphological instability may appear at the initial stage of growth, causing formation of defects. Experimental evidence has been found that supersaturation and surface kinetics are responsible for the polytype stability, while growth front and growth mode address defect reduction. An explanation of the findings has been suggested. It has been shown that starting the growth with a relatively low growth rate ( ≈ 100 μm/h ) can be beneficial for the crystal quality.
AlGaN Microwave Power HFETs on Insulating SiC Substrates
Authors: Sullivan Gerry , Gertner Ed , Pittman Richard , Chen Mary , Pierson Richard , Higgins Aiden , Chen Qisheng , Yang Jin-Wu , Smith R. Peter , Perez Raul , Khan Abdur , Redwing Joan , McDermott Brian 
Published: April 2011

ABSTRACTAIGaN HFETs are attractive devices for high power microwave applications. Sapphire, which is the typical substrate for AlGaN epitaxy, has a very poor thermal conductivity, and the power performance of AlGaN HFETs fabricated on sapphire substrates is severely limited due to this large thermal impedance. We report on HFETs fabricated on high thermal conductivity electrically insulating SiC substrates. Excellent RF power performance for large area devices is demonstrated. On-wafer CW measurements at 10 GHz of a 320 micron wide FET resulted in an RF power density of 2.8 Watts/mm, and measurements of a 1280 micron wide FET resulted in a total power of 2.3 Watts. On-wafer pulsed measurements, at 8 GHz, of a 1280 micron wide FET resulted in a total power of 3.9 Watts. Design of a hybrid microwave amplifier will be discussed.
Thick Oxide Layers on N and P SiC Wafers by a Depo-Conversion Technique
Authors: Zhang Q. , Madangarli V. , Khlebnikov I. , Soloviev S. , Sudarshan T. S. 
Published: April 2011

ABSTRACTThe electrical properties of thick oxide layers on n and p-type 6H-SiC obtained by a depoconversion technique are presented. High frequency capacitance-voltage measurements on MOS capacitors with a ∼ 3000 Å thick oxide indicates an effective charge density comparable to that of MOS capacitors with thermal oxide. The breakdown field of the depo-converted oxide obtained using a ramp response technique indicates a good quality oxide with average values in excess of 6 MV/cm on p-type SiC and 9 MV/cm on n-type SiC. The oxide breakdown field was observed to decrease with increase in MOS capacitor diameter.
Preparation of Conductive Tungsten Carbide Layers for SiC High Temperature Applications
Authors: Romanus H. , Cimalla V. , Ahmed S. I. , Schaefer J. A. , Ecke G. , Avci R. , Spiess L. 
Published: April 2011

ABSTRACTThin tungsten carbide films of different compositions were prepared by DC magnetron sputtering of tungsten and carbon and subsequent annealing in different environments. The onset of carbide formation was around 800°C. Annealing in a pure hydrogen ambient generally results in carbon depletion in the layers with the formation of a dominant W2C phase. Adding propane enhances the carbon content in the layers and stimulates the formation of the WC phase. On silicon nitride substrates, variation of the propane concentration in an annealing environment allows a continuous alteration of the layer structure between polycrystalline single phase WC and a mixed layer with dominant W2C and with it, the adjustment of different values of the electrical resistance. In contrast, on thin (100)SiC layers a textured W2C phase was grown after annealing in propane/hydrogen at 900°C whereas at higher temperatures the formation of silicides was observed. In addition, the chemical composition and the temperature dependence of the electrical specific resistance were investigated and are also discussed.
In Situ Surface Passivation of GaAs by Thermal Nitridation using Metalorganic Vapor Phase Epitaxy
Authors: Sun Jingxi , Himpsel F. J. , Ellis A. B. , Kuech T. F. 
Published: April 2011

ABSTRACTAn ammonia-based, in situ passivation of GaAs surfaces conducted within a metalorganic vapor phase epitaxy reactor is present. The shift of the GaAs surface Fermi level, and hence the surface charge density, resulting from this in situ passivation, has been studied using photoreflectance (PR) spectroscopy. Samples consisting of an undoped GaAs layer on highly doped n-GaAs (UN+) and p-GaAs (UP+) structures allow for the exact determination of the surface Fermi level position using PR These structures were grown by MOVPE and in situ thermal nitridation was performed after growth within the MOVPE system without exposure to the air. After nitridation, the surface Fermi level can be shifted by ∼ 0.23 eV towards the conduction band edge for UN+ structures and by ∼ 0.11 eV towards the valence band edge for UP+ structures from the normally mid-gap ‘pinned’ positions.
Synthesis and Characterization of Lithiated Nickel Based Metal Oxides as Positive Electrode Materials for Lithium Ion Batteries
Authors: Fujitani S. , Fujimoto H. , Nohma T. , Nishio K. 
Published: April 2011

ABSTRACTLiNi1−xCoxO2(x=0.2, 0.3, 0.4) was synthesized through a sintering process from two different types of source materials of nickel and cobalt, namely each respective hydroxide and oxide, and composite hydroxide. Influence of the difference on charge-discharge characteristics, crystal structure and distribution of the metal elements was investigated.The composite hydroxides formulated in Ni1−xCox(OH)2 as the source material brought better homogenized composite lithiated nickel based metal oxides exhibiting the larger specific discharge capacity. Further modification of LiNi0.6Co0.4)2 by manganese through sintering from the composite hydroxide including manganese brought a good charge-discharge cycle performance as well as a high discharge capacity of 160mAh/g level.A cylindrical test cell of 18mm in diameter and 65mm in height using the LiNi0.6Co0.3Mn0.1O2 exhibited discharge capacity of 1700mAh which is larger than that using LiCoO2, and also exhibited a competitive charge-discharge cycle performance to commercialized lithium ion batteries.
Characterization of Creep Behavior of SrCoo.8 Feo.203-x
Authors: Ajkic G. , Eeler L. , Alama K. 
Published: April 2011

ABSTRACTIn order to achieve commercial utilization, oxygen separation membranes and solid oxide fuel cells must be able to maintain their mechanical integrity over acceptable life-time periods. This imposes a need for characterization of mechanical behavior of the materials used under operating conditions (high temperature and low stress), in order to identify mechanisms that lead to mechanical degradation during operation. In this study, a series of compressive creep tests on rectangular specimens of SrCO0.8Feo.2O3-x of different grain sizes (2.4 to 6.8 microns) is performed in air, covering a temperature range of 850 to 975 °C and stress range of 10–20 and 40–50 MPa. In the high stress range the material has been found to render temperature dependent stress exponents (2.2 to 2.9) and high steady-state strain rates. In the low stress range the stress exponent has been found to be dose to unity (1.1 to 1.3) indicating diffusion controlled creep. The activation energy appears to assume two different values depending on operating temperature region, 457 kJ/mole below 925 OC and 268 kJ/mole above 925 OC. These values, being much higher than that for oxygen diffusion (<100 kJ/mole) indicate cation diffusion controlled creep. The shift in the value of activation energy indicates a shift in the slowest moving (rate-controlling) species between A and B cation sites. The inverse grain size exponent has been found to be dose to unity.
Porosity in Polysilsesquioxane Xerogels
Authors: Baugher Brigitta M. , Schneider Duane A. , Loy Douglas A. , Rahimian Kamyar 
Published: April 2011

ABSTRACTPolymerization of organotrialkoxysilanes is a convenient method for introducing organic functionality into hybrid organic-inorganic materials. However, not much is known about the effects of the organic substituent on the porosity of the resulting xerogels. In this study, we prepared a series of polysilsesquioxane xerogels from organotrialkoxysilanes, RSi(OR′)3, with different organic groups (R = H, Me, Et, dodecyl, hexadecyl, octadecyl, vinyl, chloromethyl, cyanoethyl). Polymerizations of the monomers were carried out under a variety of conditions, varying monomer concentration, type of catalyst, and alkoxide substituent. The effect of the organic substituent on the sol-gel process was often dramatic. In many cases, gels were formed only at very high monomer concentration and/or with only one type of catalyst. All of the gels were processed as xerogels and characterized by scanning electron microscopy and nitrogen sorption porosimetry to evaluate their pore structure.
A New Route to Prepare Hard and Anti-Scratching Coatings at Room Temperature
Authors: Liu Yanjing , Claus Richard O. , Rosidian Aprillya , Zeng Tingying 
Published: April 2011

ABSTRACTNanocomposites of transparent, multilayer structures of different thin-films have been fabricated on single crystal silicon and quartz substrates by the new deposition technique called electrostatic self-assembly (ESA) method. The method is based on the alternating adsorption of anionic and cationic polyelectrolytes in the aqueous forms. The films were then characterized by UV/Vis spectroscopy, ellipsometry, and nano-indenter. A linear behavior of both optical absorption and film thickness as the number of bilayers increases was observed, which indicated the formation of homogeneous and uniform thin-films on both substrates. The study also observed that the films prepared by this novel method have some improved mechanical properties.
Materials With Improved Properties From Polymer-Ceramic Nanocomposites
Authors: Kuchta Frank-Dieter , Lemstra Piet J. , Keller Andrew , Batenburg Lawrence F. , Fischer Hartmut R. 
Published: April 2011

ABSTRACTIn order to link the fundamental research field of polymer crystallization with the technical important field of composite materials polymer-layered silicate nanocomposites from polyethylene (PE) are prepared and their morphology and properties are investigated. The effect of an external confinement introduced by highly anisotropic silicate layers of organically modified clay minerals on crystal growth and nanocomposite properties has been studied. The prepared nanocomposites of organically modified clay minerals and PE exhibit not only a homogeneous distribution of individual silicate layers but also of tactoids. The isothermal crystallization rate of PE in the corresponding nanocomposite at 120 °C is increased in the composite material due to the action of the silicate layers. A significant effect on crystal phase has not been observed so far but from X-ray experiments, however the crystal size seems to be influenced. The thermal stability of the nanocomposites is significantly enhanced and the decomposition mechanism has been changed due to the presence of the layered silicates within the host polymer acting as a barrier for the diffusion of small molecules like oxygen. Due to the none permanent attachment of the polymer chains to the silicate surface the thermal-mechanical properties are only moderately enhanced at low temperature while the glass transition temperature remains unaffected.
Praseodymium and Neodymium-Based Nanocrystalline Hard Magnetic Alloys
Authors: Davies H.A. , Harland C.L. , Betancour R.J.I. , Mendoza S.G. 
Published: April 2011

ABSTRACTThe magnetic properties of nanophase exchange enhanced RE-Fe-B based alloys ribbons prepared by melt spinning are presented and discussed. The alloy systems investigated include NdyFe94−yB6 and PryFe94−yB6, for y within the range 6-20 at%, and the data are compared in the context of the larger anisotropy field for the Pr2Fe14B phase in comparison with Nd2Fe14B. Experimental studies are also reported for nanophase (Nd-Pr)- Fe-B alloys with various proportions of Nd:Pr, to investigate the increase in coercivity of NdFeB by partial substitution of Nd by Pr, and for (Nd, Pr)-(Fe-Co)-B-based systems, to study the degree to which the remanence enhancement can be maintained for alloys in which Co substitutes for Fe to increase the thermal stability.
Structure And Magnetic Properties Of Fe-N Thin Films Grown By Ecr Deposition
Authors: Németh S. , Akinaga H. , Boeve H. , Bender H. , Boeck J. De , Borghs G. 
Published: April 2011

ABSTRACTThe growth of FexNy thin films on GaAs, In0.2Ga0.8As, and Si02/Si substrates using an ultra high-vacuum (UHV) deposition chamber equipped with electron cyclotron resonance (ECR) microwave plasma source is presented. The structural properties of the deposited films have been measured using various techniques as x-ray diffraction (XRD), Auger electron spectroscopy (AES), and transmission electron microscopy (TEM). The results of XRD measurements show that the films consist of a combination of α-Fe, α'-Fe, γ-Fe4N, and α”- Fe16N2 phases. The depth profiles, calculated from the Auger peak intensities, show a uniform nitrogen concentration through the films. The TEM reveals a columnar structure of these films. The properties of the different Fe-N layers have been exploited in the fabrication of Fe(N) / FexNy / Fe trilayer structures, where Fe(N) means a slightly nitrogen doped Fe film. The magneto-transport properties of this trilayer structure grown on In0.2Ga0.8As substrates are presented.