bluuebunny/crossref_metadata_2025_split huggingface dataset:
Room Temperature Magnetoresistance in LaxCaYMnO3 Thin-Films Deposited by Liquid Delivery Chemical Vapor Deposition
Authors: Studebaker D. , Todd M. , Doubinina G. , Seegal C. , Baum T. H. 
Published: April 2011

ABSTRACTLiquid delivery, metal-organic chemical vapor deposition (MOCVD) was used to deposit high quality, A-site deficient crystalline films of LaxCayMnO3 where x + y < 1. The properties of the deposited thin-films are strongly dependent upon the film stoichiometry and display magnetoresistance repsonses at or above room temperature. Using Ca doped A-site deficient thin-films, we can shift the metal to insulator transition (Te) in a controlled manner to temperatures that are useful for commercial applications. Further, these films exhibit useful magnetoresistance at room temperature in relatively small applied magnetic fields.
Boron Nitride Materials for Tribological and High Temperature High Power Devices
Authors: Badi N. , Tempez A. , Starkov D. , Medelcr N. , Bensaoula A. , Kulik J. , Klimentov S. M. , Garnov S. V. , Ageev V. P. , Ugarov M. V. , Lee S. , Perry S. S. , Waters K. , Shultz A. 
Published: April 2011

ABSTRACTBoron nitride thin films on sapphire substrates were investigated for their tribological and optoelectronic applications. A gridless end Hall gun source and an electron cyclotron resonance (ECR) source were used for nitrogen species delivery while pure boron was evaporated at a rate of 0.2 Å/s. The surface stability of these thin films was investigated by high temperature annealing. Atomic force microscopy (AFM), friction force microscopy (FFM), and Knoop microhardness measurements were performed on the materials in order to assess their merits as tribological coatings. Finally, BN thin films were subjected to laser transient photoconductivity (TPC) experiments to determine both their optical laser damage threshold as well as their photoconductivity characteristics. For both single-pulse shot and multiple-pulse irradiation regimes, preliminary tests showed the higher the ion beam current used during growth (70–150 mA), the higher the optical damage threshold. The lower damage threshold was typical of BN films grown using an ECR plasma source and was measured to be in the range of ∼50 MW/cm2. Optical damage of films grown at ion beam currents above 100 mA was not observed at laser intensities up to few hundreds MW/cm2. A multiphoton excitation technique was utilized to obtain PC signals from this wide band gap material and preliminary results show that unusual PC voltage amplitudes as high as 0.5 V were observed.
Four Revolutions in Diamond Synthesis: The Vindication of Edisonian Chemistry
Authors: Roy Rustum 
Published: April 2011

ABSTRACTCareless claims by scientists are often expanded further by journalists and grossly distort the scientific “truths” passed on to the public and policy maker. Recently, such overclaims have invaded the field of materials synthesis.The real first principles of materials synthesis, based on the work of V.M. Goldschmidt (and Linus Pauling), have proved to be, and continue to be, very successful. By combining such principles with Edison's methodology of careful observation, precise experimentation and rapid feedback, thousands of new (inorganic) phases have been, and continue to be made (since 1948, several hundred from our own laboratory), producing dozens of useful, widely commercialized materials.In contrast, in spite of seventy years of trying, the so-called “first principles” calculations (from the quantum mechanics of cores and electrons) have utterly failed to actually predict and synthesize a single new material or add anything to the deep and reliable insights of well known chemical theories. It is clear that what students and researchers in contemporary materials synthesis need most is a thorough grounding in crystal chemistry and phase equilibria (including metastable equilibria).The history of the “C3N4” failure, as a harder than diamond candidate, is prototypical of the”calculating” approach to synthesis. It is contrasted with short summaries on four recent real advances into completely new processes for diamond synthesis.
Sol-Gel Precursors and the Oxygen Storage Capacity of PrOy-ZrO2 Materials
Authors: Narula C. K. , Taylor K. L. , Haack L. P. , Allard L. F. , Datye A. , Sinev M. Yu. , Shelef M. , McCabe R. W. , Chun W. , Graham G. W. 
Published: April 2011

ABSTRACTThe gels derived from mixtures of Pr(OiC3H7)3 and Zr(OiC3H7)4•iC3H7OH, upon hydrolysis and pyrolysis, furnish single-phase PrOy-ZrO2 materials crystallized in the fluorite structure. These materials can be coated onto high-surface-area γ-alumina powders or deposited onto dense α-alumina coupons in the form of thin films from a solution of parent alkoxides modified with 2,4-pentanedione in THF. The fluorite structure of the PrOy-ZrO2 in the films appears to be thermally stable in air up to 1200°C. Temperature-programmed-reduction (TPR) measurements show that the bulk PrOy-ZrO2 material with a Pr. Zr molar ratio of 1:1 can store and release oxygen while that with a molar ratio of 1:3 cannot.The precursors play an important role in determining phase composition of the resulting PrOy-ZrO2 material. A mixture of monoclinic and cubic or tetragonal phases was found in PrOy-ZrO2 prepared from a new single-source heterometallic alkoxide, Pr2Zr6(μ4-O)2(μ-OAc)6(μ-OiPr)10(OiPr)10, whereas a mixture of cubic and tetragonal phases was present in PrOy-ZrO2 made previously by coprecipitation from aqueous solutions of the metal nitrates.
The Partial Oxidation of Methanol by MoO3(010) Surfaces with Controlled Defect Distributions
Authors: Smith Richard L. , Rohrer Gregory S. 
Published: April 2011

ABSTRACTAtomic force microscopy has been used to determine how MoO3(010) surfaces with controlled defect populations evolve during reactions with MeOH/N2 mixtures. The structural evolution of the freshly cleaved surface is compared to surfaces reduced in 10%H2/N2 at 400 °C. While the freshly cleaved surfaces are flat and nearly ideal, the reduced surfaces contain voids bounded by step loops where Mo atoms in reduced coordination are found. In both cases, reacting the MoO3(010) surface with MeOH/N2 mixtures between 300 and 400 °C leads to H intercalation and the nucleation of acicular precipitates of HxMoO3. On the freshly cleaved surface, the H-bronze phase precipitates uniformly. On the reduced surface, the precipitates form preferentially at the void edges, where undercoordinated Mo atoms are found.
Structural and Electrical Properties of Phosphorous-Doped Amorphous Diamond
Authors: Camphausen S. M. , Myers A. F. , Bozeman S. P. , Cuomo J. J. 
Published: April 2011

ABSTRACTHard carbon films can be prepared by the condensation of energetic carbon species at or below room temperature. These amorphous films are primarily tetrahedrally coordinated and contain high fractions of sp3 bonds leading to the terminology amorphous diamond. These films have been successfully doped with phosphorus up to 1 at.%, by other researchers by using a phosphorus doped graphite target. We have also investigated evaporated phosphorus in conjuction with a filtered cathodic arc to incorporate phosphorus into the films and have successfully incorporated phosphorus up to 40 at.% into our films using this technique. XPS showed that some of the phosphorus was clustered. PEELS revealed that with an incorporation of 40 at.% of phosphorus, the sp3 content was approximately 20%.
Amorphous Diamond-Like Carbon Films Prepared by Dc Saddle-Field Glow-Discharge Method: Doping with Boron and Phosphorus
Authors: Chan W. , Allen T. , Gaspari F. , Szurmak J. , Sagnes E. , Zukotynski S. 
Published: April 2011

ABSTRACTOur preliminary results show that controllable doping of amorphous hydrogenated DLC films prepared by DC saddle-field glow-discharge technique is possible. We have found deposition conditions when the doping with boron is electrically effective.
Analysis and Modification of Amorphous and Partially-Crystalline Thin Films
Authors: DiNardo N. J. , Mercer T. W. , Martinez-Miranda L. J. , Siegal M. P. , Friedmann T. A. , Sullivan J. P. , Plank R. V. , Vohs J. M. 
Published: April 2011

ABSTRACTThin films of light atomic weight elements in amorphous, partially-crystalline, or crystalline forms have applications in a broad range of technologies. For example, amorphous tetrahedral carbon (a-tC) and polymeric thin films impact electronic materials technology as electron- and light-emitting device elements, respectively. A lack of crystallinity introduces complexity in the experimental and theoretical characterization of these materials but is not necessarily a limiting factor in their performance. While the growth process is clearly a major factor governing the physical properties of a film, interactions with the substrate are also important, so surface and interface analysis provides an important complement to bulk measurements. Currently, the fundamental and applied aspects of the atomic, electronic and vibrational structure of these complex materials are being elucidated by novel approaches combining several experimental techniques with theoretical calculations. This paper focuses on several approaches in the characterization and modification of thin films made possible by recent experimental advances. The structural and electronic properties of two model systems are considered as examples: a-tC thin films grown by pulsed laser deposition (PLD) and poly aniline thin films grown by vapor deposition. First, scanning probe microscopies and x-ray scattering are used to investigate the structural aspects of a-tC films as a function of PLD growth conditions. The possible connection of nanoscale surface modification and characterization with electron emission properties will be discussed. Second, the results of inelastic scattering spectroscopy and other surface techniques will be discussed to obtain information on both interfacial aspects of the growth of polyaniline thin films and microscopic and macroscopic aspects of electrical conductivity upon doping. Comparisons will be made with other studies that address properties of analogous crystalline systems as appropriate. A brief assessment of the broader problem of analyzing these systems will be given.
Melt Energetics at High Temperature and Pressure
Authors: Wilding Martin C. , Navrotsky Alexandra 
Published: April 2011

ABSTRACTThe physical behavior of silicate liquids at high pressure is important in modeling the dynamic processes of the deep earth. The density of the silicate liquids determines the transport properties of silicate melts and volumetric properties of silicate melts are therefore of prime importance. However, the partial molar volumes of melt components are difficult to evaluate since it is difficult to observe the molten state at high pressure. A variety of approaches are used to investigate silicate melt properties. Individual melt components can be used and complex mixing terms used to describe mixing behavior. Alternatively the melt species themselves can be investigated, although there is little information as to what these actually are. In both cases the accurate determination of the dP/dT slope of the melting curves is critical.Speciation reactions can be studied in situ at one atmosphere through high temperature calorimetry. An approach has been developed where the dissolution of melt components which are readily soluble in silicate solvents and which have a large heat effect can be used to determine the dependence of the activities of these components on melt structure. In addition the high temperature calorimetrie data can be used in combination with solution calorimetrie data at lower temperatures to evaluate the temperature-dependent stability of these melt species. These studies are independent of and complementary to spectroscopie determinations and provide a description of the temperature-dependence of melt structure at one atmosphere. Recent studies have focused on the solution of La2O3 and TiO2 in model silicate melts to assess the role of melt structure in the complexing of these components. The next obvious step is to extrapolate to high pressure. One possible approach is to combine one atmosphere data with existing melting relationships to determine the optimized melt compositions for a model natural systems. The next step is to then assess the stability of melt species from the partial molar properties and the partitioning of the elements between coexisting melts and mineral phases at pressures and temperatures of interest.
A new approach to the fabrication of “smart” near-surface nanostructure composites
Authors: Gea Laurence , Honda S. , Boatner L. A. , Haynes T. E. , Sales B. C. , Modine F. A. , Meldrum A. , Budai J. D. , Beckers L 
Published: April 2011

ABSTRACTA new method for the formation of “smart” near-surface nanoscale composites has been developed. In this approach, small precipitates of active phases are embedded in the near-surface region of the material that is to be modified by a combination of ion implantation and thermal processing. The dispersion, concentration, and microstructure of the nanocrystals formed in the substrate material can be tailored through a careful choice of processing parameters – making this approach well suited to high-value-added, high-technology applications. The applicability of this approach to forming “smart” surfaces on otherwise inactive materials was established in the case of VO2 precipitates which were embedded in A12O3 single crystals to create a medium suitable for optical applications – including optical data storage. Most recently, this concept has been extended to the fabrication of magnetic-field-sensitive nanostructured surfaces by forming magnetostrictive precipitates of materials such as Ni or RFe2 (with R = Tm, Tb, Sm) that are embedded in various single-crystal-oxide hosts. These nanostructured, active surface composites have been characterized using XRD, RBS, TEM, and magneto-optical techniques.
Nanoparticulate coating of functional ceramics by the vapor, solid and liquid phase reactions
Authors: Awano M. , Kameyama T. , Sando M. , Kuwahara Y. 
Published: April 2011

ABSTRACTMicrostructure control of ceramics is expected to produce novel functions or to improve properties. Nanocomposite powders of functional ceramics were fabricated by vapor, solid and liquid phase reactions, respectively. Superconducting bulk materials were fabricated by thermal plasma method and mist pyrolysis method. Microstructure control of powders for sintering contributed to improve the microstructure at grain boundaries and to introduce magnetic flux pinning centers, both resulted in the improvement of superconducting transport current property. On the other hand, a magnetic nanocomposite for the remote sensing of stress in structural ceramics was fabricated by sol-gel method and solid state reaction. Successfully introduced nano-dispersoids of ferromagnetic materials by the sintering of nanocomposite powders resulted in the harmonization of added functionality and proper mechanical properties. Magnetic response to applied stress in structural ceramic matrix was detected as the result of amplified magnetostriction caused by the nano-size effect on ferromagnetic dispersoids.
Synthesis of high temperature superconductive and colossal magnetoresistive surfaces on insulating particles
Authors: Kumar D. , Fitz-Gerald J. , Singh R. K. 
Published: April 2011

ABSTRACTThe surfaces of insulating alumina particles have been coated with high temperature superconducting, Yba2Cu3O7-x, and colossal magnetoresistive, Pr0.65Ba0.05 Ca0.3 Mn03-x, films. These coatings on particulate surfaces have been realized using a new technique which is based on laser assisted generation of homogeneous flux of ablated materials in front of a fluidized bed of host particles. The coated particulates have been characterized using scanning electron microscopy (SEM), energy dispersive x-ray (EDX) analysis, Auger electron spectroscopy (AES), and superconducting quantum interference device (SQUID) magnetometer.
Microstructure of Ultra High Dose Self Implanted Silicon
Authors: Zhu X. F. , Williams J. S. , Llewellyn D. J. , McCallum J. C. 
Published: April 2011

ABSTRACTThis study has investigated the microstructure of ultra high dose (∼ 1018 cm−2) self implantation into Si. Implants have been carried out into both (100) Si and pre-amorphised Si as a function of implant temperature between liquid nitrogen temperature and 350°C. Results show that high dose implantation into completely amorphous Si (a-Si) produces layers which regrow quite well during subsequent solid phase epitaxy. In contrast, implantation into crystalline Si (c-Si) or part amorphous/part crystalline Si can lead to rich and varied microstructures at elevated temperatures, even extending to porous-like structures in some cases. Strong dynamic annealing and agglomeration of points defects in c-Si is thought to be responsible for such behaviour.
A Depth Selective Mössbauer Study of ion Implanted Stainless Steel
Authors: Walter G. , Stahl B. , Nagel R. , Gellert R. , Rück D. M. , Müller M. , Klingelhöfer G. , Kankeleit E. , Soltani-Farshi M. , Baumann H. 
Published: April 2011

ABSTRACTHigh austenitic stainless steel of composition Fe62Ni2OCrl8 was implanted with Eu ions and analyzed with Depth Selective Conversion Electron Mössbauer Spectroscopy (DCEMS). DCEMS gives information about the depth profile of phases, in this case about implantation induced changes in phase composition as function of depth. The samples were complementary analyzed with Rutherford Backscattering Spectrometry (RBS) to get the element profile of the implanted ions. The main experimental result is a martensitic transformed depth region that coincides with the Eu depth distribution. The potential of DCEMS for application in the field of materials modification by implantation techniques is demonstrated.
Crack Nucleation in ion Beam Irradiated Magnesium Oxide and Sapphire Crystals
Authors: Gurarie V. N. , Jamieson D. N. , Szymanski R. , Orlov A. V. , Williams J. S. 
Published: April 2011

ABSTRACTMonocrystals of magnesium oxide and sapphire have been subjected to ion implantation with 86 keV Si− ions to a dose of 5×1016 cm−2 and with 3 MeV H+ ions with a dose of 4.8×1017 cm−2 prior to thermal stress testing in a pulsed plasma. Fracture and deformation characteristics of the surface layer were measured in ion implanted and unimplanted samples using optical and scanning electron microscopy. Ion implantation is shown to modify the near-surface structure of samples by introducing damage, which makes crack nucleation easier under the applied stress. The effect of ion dose on the thermal stress resistance is investigated and the critical doses which produce a noticeable change in the stress resistance is determined for sapphire crystals implanted with 86 keV Si−. In comparison with 86 keV Si− ions the high energy implantation of sapphire and magnesium oxide crystals with 3 MeV H+ ions results in the formation of large-scale defects, which produce a low density crack system and cause a considerable reduction in the resistance to damage. Fracture mechanics principles are applied to evaluate the size of the implantation-induced microcracks which are shown to be comparable with the ion range and the damage range in the crystals tested. Possible mechanisms of crack nucleation for a low and high energy ion implantation are discussed.
Ternary Group-III-Nitrides Grown in Movpe Production Reactors
Authors: Schoen O. , Protzmann H. , Schwambera M. , Schineller B. , Heuken M. , Schmitz D. , Strauch G. , Juergensen H. 
Published: April 2011

AbstractUsing production scale AIXTRON MOCVD systems various heterointerfaces in the GaInN/GaN system have been studied in depth. GaInN single hetero layers were investigated to optimise photoluminescence properties. Several approaches of capping GaInN/GaN with another GaN layer to develop high quality double-hetero (DH) structures were presented. Using an optimised interfacing technique we obtain device quality DH structures with state of the art composition uniformity across a 2 inch wafer
The Effect of Doping On Nitrogen Activation Energy Level In 4H-SiC
Authors: Evwaraye A. O. , Smith S. R. , Mitchel W. C. 
Published: April 2011

AbstractThermal admittance spectroscopy has been used to study the thermal activation energy of nitrogen at the hexagonal and cubic sites in 4H-SiC as function of net doping concentration. The net doping concentration- of te samples, which was determined from 1/C2 vs. V plots, ranges from 1.5 × 1014 cm−3 to 4 × 1018 cm−3. The thermal activation energy of nitrogen was determined to be Ee O.054 eV and Ee O.101 eV for nitrogen at hexagonal and cubic sites respectively for ND - NA ≤ 1016 cm−3. As the free carrier concentration increases from 1016 cm−3 to 1.0 × 1018 cm3, the thermal activation energy of nitrogen at the hexagonal site decreases from 54 meV to 24 meV. At ND - NA ≥1.0 × 10 cm−3 hopping conduction is the only conduction mechanism and has an activation energy of 3-9 meV.
Influence of Metal Contamination on Minority Carrier Diffusion Length and Oxide Charge
Authors: Sakuma J. , Okui Y. , Miyazawa H. , Inoue F. , Miyajima M. 
Published: April 2011

AbstractMany kinds of ULSI Circuit (DRAM, LOGIC, FRAM [1] etc.) are produced at the same production line to reduce the costs. So we have to control many kinds of metal contamination. We investigated the influence of metal contamination on minority carrier diffusion length and oxide charge. The metal impurities we studied are Fe, Cu, Ni, Cr, Al, Na, Ca, FRAM electrode metals (Pt, Ru), metals included in PZT ferro-electric capacitors (Pb, Zr, Ti) [2], metals added to PZT (La, Nb) [3], and metals used for SBT Ferro-electric capacitors (Sr, Bi, Ta) [4].
Deuterium Sintering of CMOS Technology for Improved Hot Carrier Reliability
Authors: Lee J. , Chen Z. , Hess K. , Lyding J.W. 
Published: April 2011

AbstractIt has been found that deuterium (D) instead of hydrogen (H) can be used to greatly strengthen the resistance of metal oxide semiconductor (MOS) transistors against hot carrier induced degradation. We have applied the new deuterium sintering process to CMOS technology and have obtained significantly improved hot carrier reliability resulting from the isotope effect. We will present a summary of these lifetime improvements from five different transistor structures of five different manufacturers, as well as the physical and electrical characterizations of the deuterium sintering process.
Defect Formation During Sublimation Bulk Crystal Growth of Silicon Carbide
Authors: Ohtani Noboru , Takahashi Jun , Katsuno Masakazu , Yashiro Hirokatsu , Kanaya Masatoshi 
Published: April 2011

AbstractThe defect formation during sublimation bulk crystal growth of silicon carbide (SiC) is discussed. SiC bulk crystals are produced by seeded sublimation growth (modified-Lely method), where SiC source powder sublimes and is recrystallized on a slightly cooled seed crystal at uncommonly high temperatures (≥2000°C). The crystals contain structural defects such as micropipes (hollow core dislocations), subgrain boundaries, stacking faults and glide dislocations in the basal plane. The type and density of the defects largely depend on the crystal growth direction, and many aspects are different between the growth parallel and perpendicular to the <0001> c-axis. Micropipes are characteristic defects to the c-axis growth, while a large number of stacking faults are introduced during growth perpendicular to the c-axis. We discuss the cause and mechanism of the defect formation