bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of Subgrain Boundaries in Heteroepitaxial GaN/AlN/6H-SiC Grown by Metalorganic Chemical Vapor Deposition
Authors: Liu H. X. , Ali G. N. , Palle K. C. , Mikhov M. K. , Skromme B. J. , Reitmeyer Z. J. , Davis R. F. 
Published: April 2011

ABSTRACTWe have characterized the surface morphology and luminescence properties of GaN/AlN/ SiC layers of various thicknesses using secondary electron imaging (SEI), panchromatic room temperature cathodoluminescence (CL), atomic force microscopy (AFM), optical Nomarski microscopy, and room and low temperature photoluminescence (PL). The nominally undoped GaN layers were grown by MOCVD on 0.1 m thick AlN buffer layers on commercial 6H-SiC(0001) substrates. The GaN layer thicknesses are 0.5, 1.0, 1.6, and 2.6 m. A second 1.0 m thick layer was grown by identical procedures on a 6H-SiC substrate that was first etched in H2 to remove scratches and damage due to mechanical polishing. Biaxial compressive lattice mismatch stress is present in all layers and decreases with increasing layer thickness, while PL linewidths decrease. The 1 m layer on the H-etched substrate is as relaxed as the 2.6 m layer on a non H-etched substrate, however. Pronounced surface structures, apparently corresponding to columnar subgrain boundaries, are observed on the samples on non H-etched SiC. Their typical sizes increase from about 3 to 10 m with increasing layer thickness. They are absent in the H-etched sample. These structures are generally nonradiative in CL images, although mottled contrast is also observed inside them. Similar layers doped with 3×1018 cm−3 Si do not show these features, suggesting a different microstructure.
Wavelength-Invariant Resist Composed of Bimetallic Layers
Authors: Tu Y. , Karimi M. , Morawej N. , Lennard W. N. , Simpson T. W. , Peng J. , Kavanagh K. L. , Chapman G. H. 
Published: April 2011

ABSTRACTTwo layer co-sputtered Bi over In thin films (40 nm/layer) act as a microfabrication resist with many potential applications. Their physical, chemical and optical characteristics change after laser exposures that produce a rapid thermal anneal in selected areas. Unlike organic photoresists, Bi/In is a bimetallic thermal resist whose sensitivity shows a near wavelength invariance for wavelengths from Near IR to UV. The laser-induced patterns are developed by an etch that selectively removes unexposed areas and retains converted ones. The optical density (OD) of 40 nm thick Bi/In films on quartz substrates, for example, changes from 3.3 OD to 0.37 OD in the annealed area. This has enabled the creation of direct-write photomasks for standard photoresist exposures. In this paper, the composition, morphology, and nanostructure of the resist before and after laser processing were studied in order to determine the mechanism of the laser-induced material conversion. AFM, XRD, and TEM show that the as-deposited films are polycrystalline, continuous, but with a rough, island morphology. Furnace anneals in air above the eutectic temperature (150–250°C, 3 hours) result in the formation of the tetragonal phase BiIn with a small degree of oxidation. The island morphology is maintained but there is evidence of melting and recrystallization. Transparency is much lower than after laser annealing. RBS and NRA depth profile analysis show that Bi/In films exposed to laser annealing in air contain a large fraction of oxygen and suggest that the converted film may be a BiIn0.6O6 /Bi0.3InO6 bilayer.
Ultrashallow SIMS Study of Implanted Dopants in NiSi/Si(100)
Authors: Yakovlev Nikolai L. , Wong Andrew S.W. , Lai Doreen M.Y. , Chi Dongzhi 
Published: April 2011

ABSTRACTUltrashallow doping of silicon wafers with boron was done by implantation of B+ or BF2+. Nickel silicide on them was formed by annealing of thin Ni layer. As it was revealed by secondary ion mass spectrometry, after the growth of NiSi, boron remains in Si just under the silicide layer, but fluorine accumulates in the NiSi layer. This accumulation suppresses agglomeration of the silicide.
First Principles Modeling Of High-K Dielectric Materials
Authors: Jun Gyuchang , Cho Kyeongjae 
Published: April 2011

ABSTRACTFirst-principles calculations are performed for high-K gate dielectric materials using model bulk and interface systems. Detailed electronic structures and atomic configurations are investigated for transition metal (Hf and Zr) oxide, metal doped silicate bulk system and a model Si-silicate interface system. Pseudo polymorphs of metal oxides are investigated to elucidate the underlying driving mechanisms in microscopic configurations of metal oxides and silicates in amorphous structures. We studied energetics and electronic structure of metal oxide pseudo morph with varying oxygen coordination. Dielectric constants of metal oxide and silicate materials are also investigated using the density functional perturbation theory method implemented in the ABINIT code. Electronic and dielectric properties of silica interface layers between high-κ dielectric and Si substrate are investigated leading to a confirmation that 1 nm is the physical limit of gate oxide thickness. Furthermore silica interface layer is found to have small dielectric constant of 3.4∼3.9.
Sol-Gel Derived PZT Thick Films with Nano-Sized Microstructure
Authors: Zhao C. L. , Wang Z. H. , Zhu W. , Tan O. K. , Hng H. H. 
Published: April 2011

ABSTRACTLead zirconate titanate (PZT) films are promising for acoustic micro-devices applications because of their extremely high electromechanical coupling coefficients and excellent piezoelectric response. Thicker PZT films are crucial for these acoustic applications. A hybrid sol-gel technology has been developed as a new approach to realize simple and cost-effective fabrication of high quality PZT thick films. In this paper, PZT53/47 thick films with a thickness of 5–50 μm are successfully deposited on Pt-coated silicon wafer by using the hybrid sol-gel technology. The obtained PZT thick films are dense, crack-free, and have a nano-sized microstructure. The processing parameters of this technology have been evaluated. The microstructure of the film has been observed using field-emission scanning electron microscopy and the crystallization process has been monitored by the X-ray diffraction. The thick films thus made are good candidates for fabrication of piezoelectric diaphragm which will be an essential element of microspeaker and microphone arrays.
Improved Dielectric Properties of Heterostructured Ba0.5Sr0.5TiO3 Thin Film Composites for Microwave Dielectric Devices
Authors: Jain M. , Majumder S. B. , Katiyar R. S. , Bhalla A. S. , Agrawal D. C. , Van Keuls F. W. , Miranda F. A. , Romanofsky R. R. , Mueller C. H. 
Published: April 2011

ABSTRACTIn the present work we have deposited MgO and Ba0.5Sr0.5TiO3 (BST50) thin layers in different sequences to make MgO:BST50 hetero-structured thin films. These films were characterized by X-ray diffraction and found to be highly (100) textured. The figure of merit {(C0-Cv)/(C0.tand)} of the hetero-structured films was found to be higher as compared to pure BST50 films measured at 1 MHz frequency with electric field of 25.3 kV/cm. These films were used to make eight element coupled micro-strip phase shifter and characterized in a frequency range of 13–15 GHz. The high frequency figure of merit (k factor, defined as the ratio of degree of phase shift per dB loss) measured at around 14 GHz with electric field of 333 kV/cm has been markedly improved (around 64.28 °/dB for hetero-structured film as compared to 24.65 °/dB for pure film). Improvement in dielectric properties in a wide frequency range in the MgO:BST are believed to be due to the higher densification of the hetero-structured films.
Growth of Epitaxial Site-Engineered Bi4Ti3O12-Basded Thin Films by Mocvdand Their Characterization
Authors: Funakubo Hiroshi , Sakai Tomohiro , Watanabe Takayuki , Osada Minoru , Kakihana Masato , Saito Keisuke , Noguchi Yuji , Miyayama Masaru 
Published: April 2011

ABSTRACTThin films of BIT, La-substituted BIT (BLT) and La- and V-cosubstituted BIT(BLTV) were epitaxially grown on SrRuO3//SrTiO3 substrates at 850°C by metalorganic chemical vapor deposition (MOCVD), and their electrical properties were systematically compared. All films on (100), (110) and (111)-oriented substrates were epitaxially grown with (001)-, (104)-/(014)-and (118) –preferred orientations, respectively. The leakage current density of the BLTV film was almost the same with that of the BLT film, but was smaller than that of BIT film, suggesting that the La substitution contributed to the decrease of the leakage current density especially in pseudoperovskite layer. Spontaneous polarization of the BLTV film was estimated to be almost the same with the BLT film but was smaller that that of the BIT film. This is explained by the decrease of Tc with the La substitution, while V did not contribute to the change of the Curie temperature (Tc ). On the other hand, the coercive field (Ec) value of the BLTV was smaller than that of the BIT and the BLT films. As a result, La substitution contributed to the decrease of the leakage current density together with the decrease of the spontaneous polarization due to the decrease of the Tc. On the other hand, V substitution contributes to the decrease of the defects that suppress the domain motion and increases the Ec value. Therefore, each substitution of La and V plays different roles and this contribution is remarkable for the films deposited at lower temperature.
Investigation of Domain Wall Velocity and Nucleation Rate in Polarization Switching of Epitaxial Pb(Zr,Ti)O3 Thin Films Using Piezoresponse Scanning Force Microscopy
Authors: Fujisawa H. , Yagi T. , Shimizu M. , Niu H. 
Published: April 2011

ABSTRACTDomain wall velocity and nucleation rate in 250nm-thick epitaxial Pb(Zr,Ti)O3 thin films were studied by piezoresponse scanning force microscopy (PFM). Domain growth observed after applying switching pulses shorter than the switching time can be described using the Ishibashi theory. At a pulse voltage of +5V, experimental results indicated that new nucleation occurred during the switching period, which corresponded to the Category I in the Ishibashi theory. Switching time, domain wall velocity and nucleation rate at +5V can be obtained as 70ns, 8.3m/s and 43μs-1 μm-2, respectively. As compared with experimental results reported in BaTiO3 single crystals, domain wall velocity was much smaller but nucleation rate was much larger than those in single crystals.
Mechanisms of Stress Corrosion Cracking in Si: A Hybrid Quantum-Mechanical/Molecular-Dynamics Simulation
Authors: Belkada Rachid , Ogata Shuji , Shimojo Fuyuki , Nakano Aiichiro , Vashishta Priya , Kalia Rajiv K. 
Published: April 2011

ABSTRACTWe investigate mechanisms of stress corrosion cracking in Si using a hybrid quantum-mechanical/molecular-dynamics simulation code developed recently for parallel computers. We perform the simulation for a cracked Si-model under tension (mode-I opening) with three H2O molecules around the crack front to investigate possible effects of both saturation of dangling bonds of Si with hydrogen atoms and environment molecules on the fracture initiation. Our results demonstrate existence of a path for an H2O molecule to react with Si-Si bonds at the crack front in contrast to a previous theoretical study based on the molecular orbital theory [W. Wong-Ng et al., Comp. Mater. Sci. 6, 63 (1996)].
Controlling nanoparticle template morphology: effect of solvent chemistry
Authors: Cortalezzi Maria M. , Colvin Vicki , Wiesner Mark R. 
Published: April 2011

ABSTRACTPorous solids were obtained from self-assembled deposits of silica nanoparticles used as templates to form 3-D porous membranes. The effect of the solvent chemistry on the morphology of the deposits was investigated. The parameters of interest are surface tension and ionic strength of the solvent, due to electrostatic and capillary interactions. Deposits of nanoparticles of different sizes were obtained for a variety of conditions. The deposits were imaged using SEM and showed distinctive structures for each of the solvent chemistries. The phenomenon is consistent with the DVLO theory and calculations of capillary interaction energy.
Mechanical and Structural Stability of Perovskites Membranes in Reducing Environments
Authors: Nagabhushana Nagendra , Haslebacher William F. , Venkataraman Venkat K. , Bandopadhyay Sukumar 
Published: April 2011

ABSTRACTMixed ionic electronic conducting perovskite type oxides are promising materials for potential use in various applications such as in fuel cells and membranes for air separation. An important issue in the development of the perovskites is the structural, chemical and mechanical stability of these materials at high temperatures and reducing environments (oxygen partial pressure from 0.21 to 10−17 atm) encountered in membrane reactors. SrFeO3 oxides doped with La on the A-site and Cr on the B-site showed high strength at room temperature in air. The strength degrades rapidly with an increase in temperature in air as compared to in N2 and CO2/CO environment. Fracture in the material is characterized by non-equilibrium segregation of elements within the grains. The observations provide valuable structure-property correlation as applicable to the long-term behavior of the material in advanced catalytic membrane reactors.
Mechanical and thermal properties of single crystals of ZrB2
Authors: Oka moto N. L. , Kusakari M. , Tanaka K. , Inui H. , Yamaguchi M. , Otani S. 
Published: April 2011

ABSTRACTCoefficients of thermal expansion (CTE), elastic constants and plastic deformation behaviors of single crystals of ZrB2, which possesses a hexagonal layered structure where pure Zr and pure B atomic planes stack alternatively along the c-axis, have been investigated in wide temperature ranges. While the observed elastic constants indicate highly anisotropic nature of atomic bonding being consistent with the layered structure, the observed CTE values are rather isotropic. Two operative slip systems, (0001)<1120> and on {1100}<1123>, are identified in compression tests. The observed plastic behaviors are discussed in the light of the deduced anisotropy in atomic bonding.
Calculation of thermal expansion of iron-aluminides with transition metal additives
Authors: Seletskaia Tatiana , Muratov Leonid , Cooper Bernard R. 
Published: April 2011

ABSTRACTThe addition of transition metal elements can significantly modify physical properties of intermetalic compounds. We studied the influence of Molybdenum and Vanadium additives on thermal expansion coefficient (CTE) of Fe3Al and FeAl over the wide range of temperatures. The site preference of both transition metals was determined by full-potential LMTO method within the grandcanonical formalism. At low temperatures CTEs were found directly from the FP-LMTO calculations by incorporating them into the Debye model of a solid. The obtained thermal expansion for pure Fe3Al and FeAl is within 10% of its experimentally measured values. At high temperatures we performed Molecular Dynamics (MD) simulations based on our many-body atomistic potentials. The parameters were fitted to reproduce the total energy of a crystal under various types of deformations obtained by FP-LMTO method and were tested with respect to different structures and vacancy formation energies. Our calculations show that addition of V decreases the CTEs of both iron-aluminides, while the addition of Mo makes Fe3Al DO3 structure unstable.
Bending Ductility of Heavily Cold-Rolled Ni3Al Thin Foils
Authors: Kobayashi Satoru , Demura Masahiko , Kishida Kyosuke , Hirano Toshiyuki 
Published: April 2011

ABSTRACTOur recent studies revealed that heavily cold-rolled Ni3Al foils have a good bending ductility in spite of almost no elongation in tensile test. In this paper, bending characteristics of 95% cold-rolled foils around transverse and rolling directions (TD and RD, respectively) were examined to understand the bending mechanism. Fracture elongation on the tension surface shows a large bending anisotropy: 5 % for the TD bending, while less than 1% for the RD bending. The bending ductility is due to {111}<110> slip deformation. In the TD bending, slip occurs on the slip systems operated during cold rolling, and cracks initiate along the shear bands. In the RD bending, slip occurs on the other {111} planes besides the slip planes operated during cold rolling, and fracture occurs as a result of the dislocation interaction in the both planes.
Microstructure-hydrogen sorption property relationships in LaNi5-based alloys
Authors: Inui Haruyuki , Sakamoto Hiroki , Yamamoto Tokujiro , Yamaguchi Masaharu 
Published: April 2011

ABSTRACTThe 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

ABSTRACTWe 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

ABSTRACTWe 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

ABSTRACTRaman 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

ABSTRACTThe 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

ABSTRACTWe 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

ABSTRACTThe 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.