bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low Pressure CVD Growth of AlxTi1-xN Films with Tetrakis- (Dimethylamido)Titanium (Tdmat) and Dimethyl Aluminum Hydride (DMAH) Precursors
Authors: Sun Y.-M. , Endle J. , Ekerdt J. G. , Russell N. M. , Healy M. D. , White J. M. 
Published: April 2011

ABSTRACTAlxTi1-xN film growth has been studied by a organometallic chemical vapor deposition andin-situX-ray photoelectron spectroscopy. Terakis(dimethylamido)titanium (TDMAT) and dimethyl aluminum hydride (DMAH) were used as the Ti, N and Al precursors. AlTiN film growth was observed on SiO2/Si(100) with substrate temperatures between 200 and 400 °C. The Al content in the film is controlled by the ratio of partial pressures of the two precursors in the gas phase. The metal to C to N ratio is approximately constant at 1:1:1 for most conditions studied. The chemical states of Ti, C, and N in AlxTi1-xN and titanium-carbo-nitride (TiCN) films are identical, while the Al chemical state is nitride at low, but increasingly carbidic at high Al concentration. The initial growth rate on SiO2was significantly suppressed by the presence of DMAH. At lower growth temperatures, the DMAH effect is more severe. Good step coverage was observed for AlxTi1-xN on 0.3 μm vias with a 3:1 aspect ratio.
Deposition of Ti(C,N) Thick Films by ILPCVD Starting from TDMAT
Authors: Gilles S. , Bourhila N. , Senateur J. P. , Madar R. , Levy R. A. , Blanquet E. 
Published: April 2011

ABSTRACTTi(C,N) films have been deposited from tetrakis(dimethylamido)titanium (TDMAT) and ammonia by CVD at low pressure using pulsed Injection technique (ILPCVD). This procedure allows us to easily deposit Ti(C,N) films with a good reproducibility. It is an efficient technique to control growth rates and composition of coatings. The liquid TDMAT undergoes no degradation during deposition since it is kept at room temperature. Ti(C,N) films, with fee structure and fine grains were deposited at substrate temperature varying from 200 to 500 °C. Composition of films is controlled by substrate temperature and ammonia flow rate. Growth rates as high as 2 μm/min are reached for deposition of Ti(C,N) films at low temperature (350 °C).
Nanoporous Silica for Low κ Dielectrics
Authors: Ramos Teresa , Wallace Steve , Smith Douglas M. 
Published: April 2011

ABSTRACTAs integrated circuit sizes decrease below 0.25 microns, device performance will no longer improve at the same rate as for past generations because of RC interconnect delay which becomes significant as compared to the intrinsic gate delay. The parallel approaches to partially address this fundamental problem are to use a lower resistance metal (i.e., copper instead of aluminum) and to use a dielectric material with a dielectric constant significantly below that of dense silica (∼4). Recently, considerable progress has been made in development of thin films of nanoporous silica (also known as aerogels or low density xerogels) for these ILD and IMD applications. Advantages of these materials include high thermal stability, small pore size, and similarity to conventional spin-on deposition processes, spin-on glass precursors and final material (silica). The dielectric constant of nanoporous silica can be tailored between ∼1 and 3 which allows its’ implementation at multiple technology nodes in integrated circuit manufacture starting with the 0.18 micron node.Research and development efforts at Nanoglass over the last several years have focused on; 1) simpler and more reproducible deposition processes, 2) a more complete understanding of processing-property relationships for this material, 3) scale-up of manufacturing to yield a range of precursor products with stability for at least six months and very high purity, and 4) working with customers to integrate this material into both aluminum/gapfill and copper/damascene process flows. Nanoglass has now developed a new process which considerably reduces the number of process steps and allows independent control of both film thickness and porosity. The current status of process and precursor development and device integration efforts for nanoporous silica is discussed.
One and Two color Photorefractive Processes in Sputtered WO3 Films
Authors: Bussjager Rebecca , Osman Joseph M. , Chaiken J. 
Published: April 2011

ABSTRACTAs-deposited and derivatized WO3-X films of various stoichiometry were examined in a “nonlinear interface” configuration. The optical properties of the films at 632 nm were modulated using 850 nm and 488 nm CW lasers either separately or simultaneously, Some films were modified by electrochemical reduction. Purely photoinduced changes were interpreted in the context of photoinduced chemistry involving water and/or oxygen exchange with the ambient atmosphere. Both reversible and irreversible changes were observed. Applications as either all-optical switches or logic devices are discussed.
New Liquid Precursors for Chemical Vapor Deposition
Authors: Gordon Roy G. , Chen Feng , Diceglie Nicholas J. , Kenigsberg Amos , Liu Xinye , Teff Daniel J. , Thornton John 
Published: April 2011

ABSTRACTNew precursors have been found for chemical vapor deposition (CVD) of many metal oxides. Each precursor is a mixture formed by randomly attaching a selected set of organic groups, such as the isomers of the butyl group, to a metal 2,4-pentanedionate (also known as acetylacetonate) in place of the methyl groups of the 2,4-pentanedionate ligand. Most of these new mixed metal beta-diketonates are liquids at room temperature, whereas the corresponding metal 2,4-pentanedionates are solids. In the cases where they were solids or viscous liquids, small amounts of organic solvents were added to reduce the viscosity. We have so far prepared mixed beta-diketonate precursors for barium, strontium, calcium, magnesium, aluminum, indium, tin, lead, bismuth, titanium, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, manganese, iron, ruthenium, cobalt, nickel, copper, zinc, yttrium, lanthanum and cerium.Liquid sources are much more convenient for CVD than solid sources. These liquid mixtures or solutions were vaporized by ultrasonically nebulizing the liquid into a flow of hot nitrogen carrier gas preheated to 150–250 °C. These vapor mixtures were mixed with air or oxygen and flowed over substrates heated typically to 350–450 °C. Films of the corresponding metal oxide (or carbonate, in the case of barium, strontium and calcium) were deposited on substrates of silicon or glass. Gas pressures from 20–760 Torr were used.Because a common set of ligands is used for each of these metal precursors, they can be mixed as liquids or vapors without any precipitation due to ligand exchange reactions. To demonstrate their use in forming mixed metal oxides, we have prepared films of ferroelectric barium titanate. This method should be applicable to other mixed metal oxides of current interest, such as high dielectric constant strontium titanate, ferroelectric bismuth strontium tantalate, superconducting yttrium barium copper oxide, refractory yttrium zirconium oxide, second-harmonic generating barium borate, metallic lanthanum strontium cobalt oxide and magnetoresistive lanthanum strontium manganate.
Single Source CVD of LiAlO2
Authors: Koh Wonyong , Ku Su-Jin , Kim Yunsoo 
Published: April 2011

ABSTRACTWe successfully deposited LiAlO2 films on Si substrates at 400–600 °C by single source chemical vapor deposition using a heterometallic compound, Li(O'Pr)2Al(CH3)2, which contains Li, Al, and O at the same 1:1:2 ratio as LiAlO2. Li(O'Pr)2Al(CH3)2 is sufficiently volatile to be vapor-transported at 50 °C. Elastic recoil detection and Rutherford backscattering spectroscopy analyses of a deposited film indicate that the film is stoichiometric (Li:Al:O = 1.0:1.0:2.0) and contains a few atomic percent hydrogen (5 %) and carbon (2 %). Depth profile analysis of X-ray photoelectron spectroscopy also confirms the 1:1 ratio of metal contents in the films. As-deposited films were amorphous, however, crystallized to β- or γ-LiA1O2 after annealing at 950 °C.
On Extended X-Rays Absorption Fine Structure Characterisation of Iron Platinum Clusters
Authors: D'Agostino G. , Filipponi A. , Verrazzani A. , Vitulli G. 
Published: April 2011

ABSTRACTPresent paper reports on Extended X-rays Absorption Fine Structure (EXAFS) Spectroscopy characterisation of Fe/Pt clusters. Samples of different nominal iron contents (FePt4 and FePt2) have been prepared and characterised by direct measurements of absorption coefficient at Pt L3 and Fe K edges. Catalysts were prepared by precipitation from suitable mixing (in the appropriate stoichiometry) of mesitylene suspentions containing small clusters of either platinum or iron. Single species suspention, in turn, were prepared by vapor metal deposition.Catalitic activity of prepared samples was tested on cinnammic aldehyde. As a general result, platinum clusters exhibit activity in the hydrogenation of both carbon double bond and aldehyde group with a preference for the latter. Iron addition to the pure platinum catalyst reverts the selectivity while leaving the catalitic activity almost unchanged.The present paper represents a temptative to achieve structural information on Fe and Pt short range environments, thus providing insights on the dynamics of the catalytic process.
Humidity Effects on the Electrical Properties of Epitaxial Rutile Thin Films
Authors: Burgess D. R. , Morris Hotsenpiller P. A. , Kryliouk O. , Anderson T. J. 
Published: April 2011

ABSTRACTThin films of (001) and (100) oriented rutile phase TiO2, undoped or doped with Ga or Nb, have been grown using the MOCVD technique on sapphire substrates for use in studies of the effects of humidity on the electrical properties of rutile, lbe crystallographic and microstructural quality of the films decreases with increasing Ga and Nb concentrations. Heteroepitaxy is, however, maintained with Ga or Nb concentrations up to 4.5 at% for the (001) orientation and to 0.5 at% Ga for the (100) orientation. The electrical properties of the (001) oriented rutile films have been characterized from room temperature to 225 °C in dry and humid, N2 and air atmospheres. At constant temperature in dry atmospheres, the conductance of the Nb-doped rutile films is greater than that of the undoped, which is greater than the conductance of the Ga-doped films. The activation energies for conduction in die Nb-doped and undoped rutile films in dry atmospheres are similar (∼0.1 eV), whereas the activation energy in Ga-doped films is much greater (∼0.8 eV). The effects of humidity in reducing the resistance of rutile is greatest in the Ga-doped and very min (∼150 Å) undoped films. Humidity is observed to have similar effects on both the (001) and (100) oriented 0.5 at% Ga-doped films.
Textural and Acidic Properties of Mixed Alumina-Silica Oxides Prepared with Commercially Available Sols
Authors: Monaco Steven J. , Ko Edmond I. 
Published: April 2011

ABSTRACTIn this study we have used commercially available preformed sols as building blocks to systematically explore the effects of composition, particle size, and packing on the textural and acidic properties of alumina-silica. We have prepared single oxides and alumina-silica mixed oxides with varying Al:Si atomic ratios using commercial sols from Vista Chemical Co. (alumina) and Eka Chemicals, Inc. (silica). Simple particle packing models based on the structure and experimentally determined particle size distributions of the sols explain the textural and acidic properties of both the single and mixed oxides. Comparisons with aerogels prepared from alkoxides show that materials with different atomic-scale homogeneity can be obtained. This continuum of precursor sizes from monomer through colloid allows a measure of control over textural and acidic properties in the mixed oxides, even at a fixed composition. These results show that systematic studies using preformed sols add insight into the effect of preparation upon catalytic materials.
Redox Behavior Below 1000K of Pt-Impregnated CeO2-ZrO2Solid Solutions: An In-Situ Neutron Diffraction Study
Authors: Loong C.-K. , Short S. M. , Ozawa M. , Suzuki S. 
Published: April 2011

ABSTRACTThe Ce3+↔ Ce4+redox process in automotive three-way catalysts such as Ce-ZrO2/Pt provides an essential mechanism to oxygen storage/release under dynamic air-to-fuel ratio cycling. Such a function requires a metal-support interaction which is not completely understood. We have carried out anin-situneutron powder diffraction study to monitor the crystal structures (a mixture of a major tetragonal and a minor monoclinic phase) of 10mol% Ce-doped ZrO2with and without Pt (1wt%) impregnation under oxidizing and reducing conditions over the temperature range of 25°-700°C. The samples were heated first in flowing 2%O2/Ar from room temperature to 400°C and then in 1%CO/Ar to about 700°C. A discontinued increase of the tetragonal unit-cell volume, a decrease of tetragonality (c/a), and a change of color from light yellow to gray when changing from oxidizing to reducing atmosphere were observed only in the sample containing Pt. This result supports the model which assumes the formation of oxygen vacancies initially near the Pt atoms. As more Ce ions are reduced from 4+ to 3+ oxidation states at high temperatures, oxygen vacancies migrate to the bulk of the oxide particles.
Optical Properties of Carbon thin films Containing Nanoparticles
Authors: Chhowalla M. , Munindradasa A. I. , Lim K. G. , Amaratunga G. A. J. , Kiely C. J. 
Published: April 2011

ABSTRACTThe incorporation of carbon nanoparticles in the forms of nanotubes and bucky onions have shown to improve the mechanical properties of amorphous carbon (a-C) thin films. In this paper we report on the change in the optical properties of a-C films containg nanoparticles. The optical band gap, index of refraction and extinction coefficient are studied. The optical band gap in highly tetrahedral amorphous carbon (ta-C) is found to be around 2 eV. It decreases almost linearly with the sp2 fraction. It is theorized that the clustering of the sp2 sites leads to a reduction in the band gap. In this paper, we study the influence of large sp2 clusters in forms of graphitic nanoparticles on the optical of ta-C. We find that the optical gap remains around 1.8 eV even with the large inclusions of clustered nanoparticles. Furthermore, the gap remains close to 1.8 eV even when the sp2 fraction in the amorphous matrix is increased. The index of refraction however is found to decrease with the sp2 fraction indicating a reduction in density.
Nonvolatile Memory Effects in Doped Tetrahedral Amorphous Carbon Thin Films
Authors: Gerstner E. G. , Mckenzie D. R. 
Published: April 2011

ABSTRACTMuch interest has been shown in the use of tetrahedral amorphous carbon (ta-C) deposited by filtered cathodic arc as an inexpensive, easily produced, wide band-gap semiconductor in the fabrication of electronic devices. There has, however, been limited success in producing devices with properties that might make its use in electronic applications commercially viable, which in part may be due to the high density of electronic trap states as reflected in ta-C's rather high ESR signal of ∼ 1020 spin/g. Recent results at the University of Sydney suggest, however, that a new range of possibilities exist in the utilisation of these traps as a means of producing nonvolatile digital information storage. Devices with write times of 100 μs, read times of 100 ns, and effective memory retention times approaching 1 year, have been fabricated.
Field Emission Properties of Disordered and Partially Ordered Nano Clustered Carbon Films
Authors: Coll B. F. , Jaskie J. E. , Markham J. L. , Menu E. P. , Talin A. A. , Von Allmen P. 
Published: April 2011

ABSTRACTThe fabrication of an efficient cold cathode emitter from carbon is based on a combination of material properties, which must be carefully tailored during deposition. We present the electron emission characteristics of several carbon films deposited by cathodic arc evaporation, and their correlation with the chemical composition, microtexture and microstructure of the films. The emission threshold field voltage, emission site density, uniformity and stability of both tetrahedral amorphous carbon, nitrogen doped carbon and nanoclustered carbon films will be reviewed. We will also address issues related to the deposition method, such as substrate temperature, defect density and scalability, in connection with requirements for the fabrication of field emission displays.
High Pressure Studies of Quantum Well Emission and Deep Emission in GaInP(ordered)-GaAs Heterostructures
Authors: Kwok S. H. , Yu P. Y. , Uchida K. , Arai T. 
Published: April 2011

ABSTRACTWe report on a high pressure study of emission from a series of GaInP(ordered)/GaAs heterostructures. A so-called “deep emission” band at 1.46 eV is observed in all our samples. At high excitation power, quantum well emission emerges in only one structure where thin GaP layers are inserted on both sides of the GaAs well. From the pressure dependent emission in this sample we have determined its band alignments. The role of the GaP layers in suppressing the deep emission is elucidated.
High Pressure Elasticity of MgSiO3 Perovskite, MgO and SiO2
Authors: Karki Bijaya B. 
Published: April 2011

ABSTRACTFull elastic constant tensors (cij) of three minerals namely, MgSiO3 perovskite, MgO and SiO2, are obtained as a function of pressure up to 140 GPa using first-principles computer simulations based on the local density and pseudopotential approximations. The zero pressure values and initial pressure dependence of athermal elastic constants derived from stress-strain relations are in excellent agreement with available experimental data. We find that elastic moduli, wave velocities and anisotropy of the minerals are strongly pressure dependent, particularly, in the vicinity of the structural transformations. In the view of the present experimental limitations at realistic conditions of the inner Earth, our results for high pressure elasticity are expected to be of substantial geophysical significance. Comparisons based on compressional and shear wave velocities support the prevailing hypothesis of Mg-rich silicate perovskite dominated composition for the lower mantle.
Laser Heating of Boron Nitride and Graphite in a Diamond Anvil Cell
Authors: Eremets M. I. , Takemura K. , Yusa H. , Golberg D. , Bando Y. , Sato Y. , Watanabe K. , Amaya K. , Stephan O. , Blank V. D. 
Published: April 2011

ABSTRACTCubic, hexagonal BN, and graphite were heated with the aid of cw CO2 or pulsed YAG laser in a diamond anvil cell at pressures up to 35 GPa. The recovered samples were analyzed by high resolution and scanning electron microscopy, micro-Raman, and X-ray diffraction using synchrotron radiation. Melting of hBN and cBN was achieved. Microcrystals of hBN or cBN were grown from the fluid of BN in nitrogen or argon. Analysis of the hBN-cBN transitions in dependence on pressure showed that the hBN-cBN-liquid triple point is located at 9 GPa. In the transient region between the two phases in the same sample amorphous BN was found revealing the microscopic mechanism of diffusion-like first-order transitions. BN nanotubes growing from an amorphous state at the surface of the crystals were discovered. Under nanosecond pulse laser heating graphite transforms to a diamond-like structure. Spherical droplets and nanocrystals were condensed from the ablated carbon. A compound of nitrogen with carbon was found.
Thermodynamics and Growth of GaN Single Crystals Under Pressure
Authors: Porowski S. , Grzegory I. , Krukowski S. 
Published: April 2011

GaN is recently considered as the most important material for blue and ultraviolet optoelectronics. The device structures are usually grown on foreign substrates which results in high density of dislocations above 108cm−2. The application of high N2 pressure gives a unique possibility of growing of GaN single crystalline substrates which allows to lower dislocation density in epitaxial layers by 3–4 orders of magnitude.In this paper, the results of high nitrogen pressure study of properties of Al-N, Ga-N and In-N systems are presented. The results include the phase diagrams in large range of pressures and temperatures (up to 2 GPa and 2000K) and also growth of GaN single crystals from atomic nitrogen solution in liquid gallium. The kinetic limitations of dissolution of N2 in liquid Al, Ga and In will be discussed. It follows, that the best conditions for crystal growth at available pressures and temperatures can be achieved for GaN.The high nitrogen pressure experimental system equipped with multi-zone internal furnace was used for growth of high quality GaN crystals. At present both n-type and semi-insulating substrate quality GaN crystals with surface area up to 1cm2, with dislocation density below 105 cm-2 are routinely obtained and successfully used for homoepitaxy.Some results concerning homoepitaxial growth by the MOCVD and MBE methods are shortly reviewed. In particular, it is shown that perfectly matched (strain free) GaN layers can be deposited on the highly resistive GaN:Mg substrates.
Binary self-assembled monolayers for surface control of liquid-crystal orientation: an x-ray study
Authors: Geer R. E. , Yang J. Y. , Frank C. W. 
Published: April 2011

ABSTRACTChemisorbed monolayers of decyltrichlorosilane, [11-(2-Naphthyl)undecyl]trichlorosilane, and a coadsorbed binary mixture of the two were prepared and subsequently investigated using lowangle x-ray reflectivity. Electron density profiles calculated from this data combined reveal well-defined naphthyl and alkyl regions in the [11-(2-Naphthyl)undecyl]trichlorosilane monolayer indicating a high degree of registry along the film normal. These conclusions are consistent with previous spectroscopic measurements of the same system.
Poly(styrene-b-butadiene-b-styrene) self-organized Ultrathin films
Authors: Wang D. Y. , Liu F. Q. , Cao Y. A. , Liu Z. Q. , Shen D. F. , Qian X. M. , Song J. Q. , Liu Z. F. , Bai Y. B. , Li T. J. , Tang X. Y. 
Published: April 2011

ABSTRACTDirect images of the surface morphology of a series of the poly(styrene-b-butadiene-b-styrene) (SBS) ultrathin films have been obtained by atomic force microscopy (AFM). These films were formed under kinetic control. The resulting films consist of 25 nm-diameter spherical structures and/or cylindrical ones. These structures are surprisingly different fi-om alternative-lamellar structures which should be formed under annealed conditions because of the nearly equal length of two blocks of SBS. In nonselective solvents, the surface of the cast solution layer induces the copolymers to self-organize into micelle consisting of a polystyrene (PS) core and a polybutadiene (PB) shell in order to decrease film surface energy. The final structures depend on the property of the solvent used and filn-forming condition.
Microparticles of Functionalized Polylactide Copolymers
Authors: Gonsalves K. E. , Jin S. , Baraton M-I 
Published: April 2011

ABSTRACTMicroparticles of poly(lactide) (PLac) and its copolymers with the amino acids, serine (P(Lac- Ser)), and aspartic acid (P(Lac-Asp)), respectively, were synthesized using the solvent evaporation microemulsion technique. Poly(vinyl alcohol) (PVA) was added as a non-ionic surfactant to stabilize the particles. The particle sizes are in the range of 200 nm. The surface of the particles was characterized by FTIR transmission spectroscopy under evacuation at room temperature and at 200°C. Hydroxy groups originating from PVA exist on the surfaces of the particles and they were observed at 3506 cm−1. Free hydroxy groups originating from the serine residue pendant to the copolymer P(Lac-Ser) backbone were observed at 3396 cm−1. Also, free carboxylic acid groups pendant to the copolymer P(Lac-Asp) backbone, originating from the aspartic acid residue, were observed at 3387 cm−1. The appearance of the free hydroxy or carboxylic acid groups in the IR spectra also showed that these hydrophilic functional groups moved to the surface of the particles in the process of microemulsion.