bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural, Electrical, and Optical Properties of Erbium-Doped Epitaxial BaTiO3 Films Grown by RF Sputtering
Authors: Barrios Pedro , Li Cheng Chung , Kim Hong Koo , Blachere Jean 
Published: April 2011

AbstractWe have investigated the epitaxial growth of Er-doped BaTiO3 films using rf magnetron sputtering. The Er-doped films (0.5 - 1 μm thick) were deposited on MgO (001) single-crystal substrates at various temperatures (500 - 800 °C). The films deposited at 700 °C or above arehighly (001)- oriented with an in-plane epitaxial relationship of BaTiO3[100] ║ MgO[100], as confirmed by X-ray diffraction. The Er doped films were found to be compressively stressed, as-deposited. The amount of stress monotonically decreases as a function of the deposition temperature. The Er-doped epitaxial films show a strong room-temperature photoluminescence at 1.54 μm, which corresponds to intra-transitions of Er3+ ions. Electrical characterizationswere carried out on Er-doped BaTiO3 films that were grown on MgO with a conducting In203 buffer electrode. The measurement shows that the Er-doped BaTiO3 films are ferroelectric with a remanent polarization of 1.5 μC/cm2 and a coercive field of 40 kV/cm.
Growth and Purity of Epitaxial Compounds
Authors: Flynn C. P. , Yang M.-H. 
Published: April 2011

AbstractWe report experience in our laboratory with the growth of epitaxial compounds using molecular beam epitaxy. These include the L12 structures, Laves phases, perovskite, bixbyite and spinels, with complicated structures and up to 80 atoms per cell. In many cases the growth takes place with surprising ease, even though the complexity of the process verges on self assembly. The paper describes diffusion measurements in epitaxial MgO directed towards the determination of impurity content and the level of structural defects. The synthesis of ‘ultrapure’ epitaxial MgO, and the resulting properties is described.
Modification of Epitaxial Oxide Films with Ion Implantation
Authors: Hong S. H. , Miller J. R. , Ma Q. Y. , Yang E. S. , Fenner D. B. , Yang C. Y. , Budnick J. I. 
Published: April 2011

AbstractIon implantation is used to modify the properties of oxide (YBCO and YSZ) thin films. Both superconducting and dielectric epitaxial oxide films, grown by laser ablation, are studied. The properties of the implanted oxide films are characterized by SIMS, XPS, DC resistivity and AC susceptibility measurements. By introducing reactive ions into superconducting oxide films, the conductivity of the material is inhibited possibly due to the interaction of the implanted ions with oxygen originally bound to the copper atoms. Al, Si, Ag and Ca ions are implanted into epitaxial YBCO films with injection energies ranging from 50 - 100 KeV and doses ranging from 1×1015 - 1×1016/cm2. XPS analysis shows that the implanted Si ions form SiOx. The inhibition method has been applied to the fabrication of superconducting electronic devices, such as SQUIDs. Dielectric oxide films are doped by the implantation of conductive and non-conductive ions. YSZ films are doped with Ag and Si ions and the ions are found to increase the conductivity.
Study of Grain Boundaries in YBCO Thin Films Using Microraman Spectroscopy
Authors: Martinez O. , Jimenez J. , Martin P. , Chambonnet D. , Degoy S. , Belouet C. 
Published: April 2011

AbstractMicroRaman spectroscopy allows to identify the presence of c| and c⊥ oriented grains in YBCO thin films. This is achieved by the observation of two Raman modes associated with the oxygen sublattice vibrations, ˜500 cm−1 and ˜338 cm−1. The relative intensity of these Raman modes is related to the presence of c⊥ and c⊥;. oriented grains. Using the high lateral resolution of the Raman microprobe (<1 μm) some needle shaped grains of the films were scanned. The different Raman parameters were analyzed, showing noteworthy transformations at the [c|;]/[c⊥] boundaries. In particular the Raman mode corresponding to the out of phase O (2)– O(3) in plane vibrations (˜338 cm−1) was found to be narrowed, which should account for a decoupling of the phonon with the electronic continuum.
Large Area Uniform Deposition of YBa2Cu3O7 Thin Films by a 90° Off-axis Sputtering Technique
Authors: Rao R. A. , Gan Q. , Eom C. B. 
Published: April 2011

AbstractLarge area uniform deposition of Yba2Cu3O7 (YBCO) thin films on 8 inch diameter wafers, using a 3 inch diameter sputtering target and optimized substrate rotation in a single target 90° off-axis sputtering technique, is reported. The variation in thickness, composition and superconducting properties was studied as a function of substrate position on stationary and rotating substrates. The films deposited from a 3” target on rotating substrates displayed uniform thickness (< ±5% variation) and composition (< 2.3% deviation from target stoichiometry) and a consistently high transition temperature ( Tc > 88.3°K) over an 8” diameter area.
Epitaxy and Magnetotransport Properties of La0.8Sr0.2MnO3 Films Synthesized by Both Pulsed Laser Deposition and Novel Chemical Routes
Authors: Modak A. R. , Krishnan Kannan M. 
Published: April 2011

AbstractLa0.8Sr0.2 MnO3 thin films with different microstructural characteristics were prepared by both pulsed laser deposition and a novel polymeric sol-gel process. For both techniques, polycrystalline films were obtained on Si(100) with a native oxide surface but epitaxial and highly oriented growth could be induced on lattice-matched LaAlO3(100) substrates. Whilst the overall magnetization and magnetoresistance behavior as a function of temperature and applied field were consistent with recent results, i.e. a semiconductor-to-metal transition accompanied by an antiferromagnetic-to-ferromagnetic transformation and large magnetoresistance at the resistance peak temperature, the properties of the films were significantly different depending on the microstructure, epitaxy and polycrystallinity. Detailed microstructural characterization of the films are presented and correlated with their magnetic/magnetotransport properties.
Epitaxial Growth and Physical Properties of La1-xCaxMnO3-δ Thin Films on MgO(001) Substrates
Authors: Gu J. Y. , Kim K. H. , NOH T. W. , Lee Jeong Soo , Jeong Young Woo , Jo W. 
Published: April 2011

AbstractPerovskite La1-xCaxMnO3-δ (LCMO) thin films with a wide range of x, i.e., 0.0 ≤ x ≤ 0.6, were deposited on MgO(001) substrates using a pulsed laser deposition (PLD) technique. Epitaxial La0.7Ca0.3MnO3-δ/MgO thin films were able to be grown under a condition such as 1.5 ∼ 2.1 J/cm2 of a laser fluence, 650 ∼ 750 °C of a substrate temperature, and 100 ∼ 300 mtorr of an oxygen pressure. X-ray pole figures and electron diffraction pattern showed that the LCMO films were grown epitaxially on MgO(001). Rutherford Backscattering Spectroscopy measurements investigated that the epitaxial LCMO films have compositions similar to those of targets, demonstrating the PLD is a useful technique to get films with complicated chemical compositions. Various physical properties, including resistance, R, magnetoresistance, ΔR/R(H=0) ≡ (R(H)-R(0))/R(O), and magnetization, M(T), were measured. The LCMO thin films with 0.2 ≤ x ≤ 0.5 had both semiconductor-metal and ferromagnetic ordering transitions, whose temperatures are located close to each other. These physical properties were explained in terms of the magnetic polaron model.
Filling Dependence of Magnetoresistance in Perovskite-type Manganese Oxide Films
Authors: Kasail Masahiro , Kuwaharal Hideki , Moritomol Yutaka , Tomioka Yasuhide , Tokura Yoshinori 
Published: April 2011

AbstractFilling dependence of magnetotransport properties was investigated in Ndl−xSrxMnO3 films. Hysteretic behavior was observed in temperature dependencies of resistivity for restricted filling of x-0.35 and 0.50, indicating the occurrence of a first-order phase transition at low temperatures. The transition gives rise to a high-resistivity state which collapses to low-resistivity state under an external magnetic field. Change in resistivity by applying magnetic field was more than a order of magnitude. Origin of colossal magnetoresistance (CMR) is briefly discussed in terms of such a first-order phase change induced by a magnetic field.
Grain Boundaries of Controlled Geometry in ZnO Films Grown by Chemical Vapor Deposition: Undoped and Bi -Doped Boundaries
Authors: Majid I. , Liu Y. , Balluffi R. W. , Sande J. B. Vander 
Published: April 2011

AbstractWe describe a chemical vapour deposition technique for the controlled growth of ZnO films, containing grain boundaries which are suitable for detailed atomic resolution studies. Using this technique, we have grown; (1) random polycrystalline, (2) highly textured polycrystalline and (3) nominally single crystal films Also, a technique for doping the grain boundaries in these specimens with Bi by an “in-diffusion” method is demonstrated. The grain boundary atomic level structure and chemistry is studied by means of High Resolution Electron Microscopy (HREM) and STEM/EDX microanalysis. Some results obtained from boundaries in textured polycrystalline films which have the c-axes in neighboring grains lined-up to ˜1 ° are described.
A Study of Copper Oxide Films Fabricated by Pulsed Laser Deposition
Authors: Leuchtner R. E. , Hristakos L. S. 
Published: April 2011

AbstractCopper oxide films were grown using the pulsed laser deposition (PLD) method with either a copper metal or a copper oxide target. A variety of deposition pressures of oxygen (0.001–0.3 torr) and temperatures (350, 450, and 550°C) were explored. From x-ray diffraction analysis, epitaxial <100> CuO films were observed at 450°C and either at 0.01 or 0.1 torr for the CuO and the Cu targets, respectively. Deposition rates were measured for the two targets (Cu and CuO) as a function of laser fluence and background gas pressure and enabled a morphological study of films prepared at different laser fluences but of similar film thickness (∼0.3 μm). The number density of particulates as well as the smoothness of the underlying film surface of the CuO films varied significantly with the target composition. The CuO films from the Cu target were the smoothest and had the fewest particulates.
In-Situ Observations of Electromigration-Induced Void Dynamics
Authors: Frankovic Richard , Bernstein Gary H. 
Published: April 2011

AbstractElectromigration void nucleation and growth is a failure mechanism of integrated circuit (IC) metallization. The time-to-failure of interconnect lines depends on the void nucleation time and the void growth time. While much work has been done to model the void nucleation stage, the current understanding of the void growth stage is minimal. The importance of characterizing the void growth and motion dynamics is essential to further explain electromigration performance of IC metal interconnections.Electromigration-induced voids previously studied have been observed to grow, coalesce, and even heal, but quantitative information on these dynamics is lacking. This work uses high-resolution electron-beam lithography to define sub-micrometer voids of various sizes and shapes into gold lines in order to observe void growth and movement with respect to initial void size and shape. The electromigration-induced dynamic behavior of pre-defined voids was measured in a field-emission scanning electron microscope in-situ. Results showed these prepatterned voids can re-fill or grow, and can yield quantitative results on dynamic void behavior.
In Situ Dynamic Atomic-Level Investigation of a Weak Charge Transfer Lamellar Intercalation Process
Authors: Diebolt L. , Sharma R. , Mckelvy M. , Glaunsinger W. S. 
Published: April 2011

AbstractEnvironmental-cell dynamic high-resolution transmission electron microscopy (DHRTEM) has been used to provide atomic-level insight into lamellar reaction processes for the model weak- charge-transfer intercalation reaction of NH3with 2H-TaS2.In situintercalation was induced by exposing 2H-TaS2crystallites to controlled pressures of NH3(g) and recorded on videotape with 0.03 second time resolution. The intercalation processes observed possess a strong similarity to nucleation and growth processes. Onset occurs in either outermost or internal guest galleries, with further intercalation of the galleries progressing away from the onset layers. Randomly staged regions, containing occasional packages of short-range order, were observed to form during the growth process.
In Situ Real Time Observation of Chemical Vapor Deposition Using an Environmental Transmission Electron Microscope
Authors: Drucker Jeff , Sharma Renu , Weiss Karl , Ramakrishna B. L. , Kouvetakis John 
Published: April 2011

AbstractMaterial synthesis by chemical vapor deposition (CVD) in a number of material systems has been investigated in real time using an environmental transmission electron microscope (ETEM) with 3.8 Å resolution. Here, we will focus on two metal / insulator systems. Al CVD onto SiO2from trimethyl amine alane and Au CVD from ethyl (trimethylphosphine) gold (I), also onto SiO2. For Al deposition, dendritic growth was observed for all pressure / substrate temperature combinations investigated for growth on untreated SiO2. Subsequent to reaction of the substrate surface with TiC14, almost immediate continuous Al film growth was observed. Growth rates for the Al film could be measured in situ by monitoring the evolution of the growth front at the Al/vacuum interface. In this system, very little enhancement in the metal film growth rate was observed as a consequence of electron beam irradiation for continuous films grown after TiCl4pretreatment.. This dramatically contrasts with the case of Au CVD investigated. In this instance, growth rate enhancements of up to 150 times were observed during electron beam irradiation as compared to purely pyrolytic decomposition of the precursor on the insulator surface. This growth rate enhancement decreased monotonically with substrate temperature. We surmise that this effect is related to the ratio of precursor surface residence time prior to ecomposition to the probability of collision from the impinging electron beam.
Fabrication of Novel III-N and III-V Modulator Structures by ECR Plasma Etching
Authors: Pearton S. J. , Abernathy C. R. , MacKenzie J. D. , Mileham J. R. , Shul R. J , Kilcoyne S. P. , Hagerott-Crawford M. , Ren F. , Hobson W. S. , Zavada J. M. 
Published: April 2011

AbstractQuantum well microdisk laser structures have been fabricated in the GaN/InGaN, GaAs/AlGaAs and GaAs/InGaP systems using a combination of ECR dry etching (Cl2/CH4/H2/Ar, BC13/Ar or CH4/H2/Ar plasma chemistries respectively) and subsequent wet chemical etching of a buffer layer underlying the quantum wells. While wet etchants such as HF/H2O and HCI/HNO3/H2O are employed for AlGaAs and InGaP, respectively, a new KOH-based solution has been developed for AlN which is completely selective over both GaN and InGaN. Typical mask materials include PR or SiNx, while the high surface recombination velocity of exposed AlGaAs (∼105cm·sec-1) requires encapsulation with ECR-CVD SiNx to stabilize the optical properties of the modulators.
Siox Related Photoluminescence Excitation in Porous Silicon
Authors: Torchinskaya T. V. , Korsunskaya N. E. , Dzumaev B. R. , Sheinkman M. K. 
Published: April 2011

AbstractUsing PL, PLE, secondary ion mass spectroscopy (SIMS) and EPR investigations we show in this paper that two luminescence bands with different PL excitation spectra exist on the surface of silicon wires in PS.
Visible Luminescence from Surface-Oxidized Silicon Nanostructures: Three Region Model
Authors: Kanemitsu Yoshihiko 
Published: April 2011

AbstractWe discuss the mechanism of red luminescence from surface-oxidized Si nanostructures. The interface state between crystalline Si and SiO2 surface layer plays an essential role in efficient visible luminescence. The crystalline Si nanostructures with a disorder potential of interface states show complicated luminescence properties.
Possibility of Self-Trapped Excitons in Silicon Nanocrystallites
Authors: Allan G. , Delerue C. , Lannoo M. 
Published: April 2011

AbstractWe present semi-empirical tight-binding and ab-initio local density calculations demonstrating the (meta)stability of self-trapped excitons in silicon nanocrystallites. These are obtained not only for surface dimer bonds passivated for instance by hydrogen atoms or by silicon oxide but also for “normal” nearest-neighbors bonds. Light emission from these trapped excitons is predicted in the infrared or in the visible. We are thus led to the interpretation that part of the luminescence is due to such localized states while optical absorption is characteristic of quantum confinement effects. These conclusions should extend to other semiconductor crystallites.
Thermal Stability of GaAs/InGaP and InGaP/(In)GaAs Interfaces
Authors: Hyuga F. , Nittono T. , Watanabe K. , Furuta T. 
Published: April 2011

AbstractThermal stabilities of GaAs/InGaP and InGaP/(In)GaAs interfaces are investigated using InGaP/(In)GaAs/InGaP single quantum wells. Annealing is performed at a temperature range between 600 and 900 °C for 10 min. Positions and the full widths at half maximum (FWHM) of photoluminescence (PL) peaks are almost identical to those of as-grown ones up to 800 °C. Blue shifts of PL peaks and increased widths of their FWHM observed after 900 °C annealing are suppressed by shortening the annealing time to 0.1 sec. Annealing at 900 ‘C for 0.1 sec is sufficient to activate Si ions implanted into (In)GaAs layers. As a result, these thermal stabilities are able to provide high reliability and high performance of InGaP/(In)GaAs heterostructure MESFET ICs.
A New Method for the Electronic and Chemical Passivation of GaAs Surfaces Using Cs2
Authors: Lee Ju-Hyung , Xu Yanzhen , Burrows Veronica A. , McMillan Paul F. 
Published: April 2011

AbstractA new GaAs surface passivation method, CS2 treatment at moderate temperature was developed for effective passivation of GaAs surfaces. The CS2 treatment of GaAs surfaces at 350 °C and 10 atm leads to deposition of a homogeneous film, with a thickness of several hundred A. The passivation layer thus produced causes a significant enhancement in room temperature photoluminescence intensity and the passivation effect of the sulfide film was confirmed by Raman spectroscopy. The passivation layer remained electrically and chemically stable over a period of nine months under ambient atmospheric conditions. In-depth Auger electron spectroscopy (AES) revealed that the carbon and oxygen content in the film was negligible, whereas sulfur was uniformly distributed throughout the film. A metal-insulator-semiconductor diode whose insulating layer is produced by the CS2 treatment shows well-defined accumulation and depletion regions in its capacitance-voltage (C-V) characteristics with low hysteresis.
Characterization of the Interface Between Metal Contacts and Epilayers of Doped Silicon Carbide
Authors: George M. A. , Larkin D. J. , Petit J. , Burger A. , Morgan S. H. , Collins W. E. 
Published: April 2011

AbstractAluminum contacts on chemical vapor deposited (CVD) SiC films were studied to examine variations in the chemical, morphological and electrical properties of the samples. Nitrogen and aluminum doped substrates were prepared to give n-type and p-type SiC epilayers respectively. These preparations were examined by surface sensitive spectroscopies and by atomic force microscopy (AFM). Samples were studied both before and after the deposition of aluminum films to compare differences between SiC(p++)/metal and SiC(n++)/metal contact interfacial properties. Aluminum has generally been found to have good adherence to the n+ epilayer but do not form good ohmic contacts, while metal films deposited on p+ epilayers have had poor adherence but have been found to provide better ohmic character. AFM images revealed nanometer sized clusters, attributed to excess Si on the n+ epilayers, while no clusters were observed on the p+ epilayers. XPS studies of the as-prepared samples indicated that the n+ epilayers had higher concentrations of oxides which may enhance adhesion. The chemical composition and morphology is discussed and correlated to the electrical properties obtained for the various samples.
Gold Nanocomposites Prepared by Reactive Sputtering
Authors: Maya L. , Paranthaman M. , Thundat T. , Allen W. R. , Glover A. L. , Mabon J. C. 
Published: April 2011

AbstractReactive sputtering of gold and selected gold alloys in oxygen and nitrogen plasmas generated in a DC glow discharge was studied. Gold alloys examined were various compositions with gallium, aluminum and silicon. Gold is transported unreacted from a gold target to the substrate in a nitrogen plasma to form polycrystalline films, but gold alloys produce fine dispersions of gold in the corresponding ceramic nitride matrix which was crystalline for gallium and amorphous for silicon and aluminum. This contrasts with the behavior in an oxygen plasma which produces pure gold oxide, Au2O3, from a gold target and gold oxide-silicon oxide nanocomposites from Au/Si alloys. Gold oxide is thermally labile and reverts to the elements at 350 °C. Stress in gold oxide films was detected in the decomposition profile, volatile evolution versus temperature, as an event occurring at a lower temperature. The thermal lability of gold oxide was utilized to generate gold nanocomposites in silica with different metal loading through pyrolysis of the corresponding precursor gold oxide-silica films. The properties of gold oxide and gold nanocomposites are described.
Thermal and Mechanical Characteristics of Polyimide Based Ceramers
Authors: McDaniel P. R. , StClair T. L. 
Published: April 2011

AbstractPolymer dominated polyimide/preceramic ceramers have been prepared by two different techniques. Both methods currently offer high potential of generating a novel nanostructure with well consolidated moldings of the multiphased systems. The first method involves microencapsulation of sub-micron polymer particles of LARC• IA (Langley Research Center Improved Adhesive) in a TiO2 coating and the other method utilizes LARCTM IA amic acid and TEOS in a sol-gel process. Each has allowed for the formation of ceramers possessing properties of both inorganic glasses and organic polymers. Processing, thermal characterization, and mechanical properties of the resultant materials will be discussed.
AB-Initio Calculations of CzSil-z-yGey, Compounds for Silicon-Based Heterojunction Devices
Authors: Berding M. A. , Sher A. , Schilfgaarde M. Van 
Published: April 2011

AbstractWe present recent results on the properties of ordered group IV compounds containing carbon, silicon and germanium. Our calculations are done using a full-potential -linearized muffin-tin orbital (FP-LMTO) method within the local density approximation (LDA). Twenty-seven fully relaxed compounds represented by six different compound structures have been examined. With the exception of SiC, all compounds are found to be metastable. Two trends emerge: compounds that have carbon on a common sublattice are less unbound because of their relatively low strain, and carbon-germanium bonds are disfavored. Simple two-body (bond-length) and three-body (bond-angle) empirical fits to our first-principles results are not adequate to predict excess energies with sufficient accuracy to be reliably predictive for other structures. Some compounds have direct gaps. When carbon shares a sublattice with silicon or germanium, the large strain results in a narrowing of the band gap, and in some cases the compound is metallic. The most promising structures with the lowest excess energy contain carbon on one sublattice and do not lattice match to silicon, but match rather well to silicon carbide.