bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement and Modeling of Optical Constants for Rough Surface Diamond Thin Films
Authors: Yin Z. , Tan H. S. , Smith F. W. 
Published: April 2011

ABSTRACTThe measurement of the optical constants for a rough surface thin film is needed for CVD polycrystalline diamond films which typically have surface roughnesses of the order of tens to hundreds of nm. In this paper, we present a method for determining the optical constants n and k as well as the surface roughness σ for a rough surface diamond thin film. By using the theory of optical reflectance (R) and transmittance (T) for a thin film with incorporation of rough surface scattering factors which are functions of the surface roughness a, the following function can be obtained: R=R(n,k,σ,λ,d), T=T(n,k,σ,λ,d), and Rp=Rp(n,k,σ,λ,d), where λ and d are the incident wavelength and film thickness, respectively. Rp is the reflectance from the smooth back surface of the thin film. From the experimental data for R, T, and Rp in a range of wavelengths, the optical constants n, k, and σ can be extracted by solving the above non-linear equations using a three-dimensional Newton-Raphson technique. Examples of experimental results on diamond films and other examples of simulated results are presented to illustrate the usefulness and validity of this technique.
Bonding Silicon Devices on Diamond Heat Spreaders
Authors: Fan W. D. , Jagannadham K. , Narayan J. 
Published: April 2011

ABSTRACTWe have developed diamond heat spreaders and bonding technology to silicon device structure. Diamond films were grown on molybdenum and Si substrates using hot filament chemical vapor deposition. Tin or gold-tin solders were used for bonding. Bonding of silicon on diamond was carried out at 20 Torr with hydrogen ambient and a temperature between 300 to 400°C for half hour. The diamond films were characterized by Raman spectroscopy and scanning electron microscopy. Interfaces between silicon and diamond films Were examined by scanning electron microscopy and energy dispersive spectroscopy. Pull-tests were used to determine the strength of the bonding between the silicon substrate and the diamond film. Bonding is improved with special metallization procedure using Ti and Cu films on the silicon substrate and Ti and Au or Cu films on the diamond film. Mechanisms of improvement of bonding due to metallization layers are discussed.
High Quality Homoepitaxial Diamond Films Grown in End-Launch Type Reactors
Authors: Hayashi Kazushi , Yamanaka Sadanori , Okushi Hideyo , Kajimura Koji 
Published: April 2011

ABSTRACTHigh quality diamond films have been successfully grown, by step-flow, on (001) diamond substrates using an end-launch type chemical vapor deposition reactor. Electrical properties of as-deposited diamond films as well as the surface morphology and the film crystallinity were investigated. Optical and atomic-force microscope images indicated that diamond films consisted of atomically flat terraces and macroscopic steps running parallel to [110×l and 1×2 double-domain structure. The currentvoltage characteristics of Al-Schottky contacts to these step-flow grown diamond films showed excellent rectification properties, indicating the potential of this material for electronic applications.
Towards Large Area Diamond Substrates: The Mosaic Process
Authors: Janssen Ger , Schermer John J. , Giling L. J. 
Published: April 2011

ABSTRACTA method has been developed for producing large area single-crystal diamond plates, suitable for optical and electronic applications. It starts with orienting and closely packing a set of diamond seed crystals with (001) top faces. This assembly, or mosaic, is then joined by a single-crystal overgrowth using a CVD process. A number of assembling techniques have been tested for compatibility with homoepitaxial diamond growth by hot filament assisted CVD and/or growth and etching by the acetylene-oxygen combustion flame. Furthermore a two-step process is described. First an initial layer (20-50/μm) is deposited by hot filament assisted CVD at a low growth rate in order to bridge the gap between the seeds. Subsequently the fast growth rate of the acetylene-oxygen combustion flame is employed to increase the layer thickness (>250,μm). It was found that both the basic mosaic process as well as the two step process can produce a single-crystal diamond layer on top of mosaics consisting of seed crystals with well aligned crystallographic directions. The width of the gaps between the seed crystals (up to 25 μm) was found to be less critical, while the orientation of the side faces and the direction of the misorientation (i.e. the step flow direction) seem not to effect the successful overgrowth. Apart from the alignment of the seed crystals the most severe problem, which has to be overcome in order to obtain one single-crystal overgrowth, is the occurrence of penetration twins in the joint regions. The largest mosaic structure -up to now- overgrown by CVD consists of seven seed crystals and has a surface area slightly in excess of 1 cm2
Correlation of Electrical Properties With Defects in A Homoepitaxial Chemical-Vapor-Deposited Diamond
Authors: Han S. , Rodriguez G. , Taylori A. , Plano M. A. , Moyer M. D. , Moreno M. A. , Pan L. S. , Black D. B. , Burdette H. , Ager J. W. , Chen A. 
Published: April 2011

ABSTRACTA high-quality, low-stress 200 gim epitaxial diamond film has been grown on a 400 μm thick high-temperature-high-pressure Ila diamond. X-ray diffraction images of the film indicate that a large region of the film is fairly defect free and individual dislocations have been imaged in this region. Depth-resolved Raman results indicate that the region of the film with a low density of defects also has lower stress than in the higher defect density region. Transient photoconductivity measurements were performed on the high and low line defect density regions of the homoepitaxial diamond film to determine the effects of the stress and defect density on the combined electron-hole mobility and carrier lifetime. The correlation between the electrical properties and the x-ray diffraction imaging suggests that line defects may not be the limiting factor in the carrier transport at the present film quality
Polycrystalline Diamond, Boron Nitride and Carbon Nitride Thin Film Cold Cathodes
Authors: Pryor R. W. 
Published: April 2011

ABSTRACTRecent observations are presented on the emission of electrons from n-type polycrystalline diamond and from two new families of nitride-based cold cathode films, n-type boron nitride (BN) and n-type carbon nitride (CN). The n-type polycrystalline diamond films were synthesized by MPECVD. The BN and CN n-type films (∼150 nm) were synthesized by reactive laser ablation on n-type polycrystalline diamond (∼24 μm) on (100)Si.Emission current densities have been measured as high as 119 ma cm−2. Extraction fields have been observed to range from ∼0 V μm−1 up. The diamond films show a field activated thermionic behavior. Both the BN and the CN films show a power-law current density / applied field response implying a negative electron affinity (NEA) type behavior.
Theory of Electron Emission and Transport Properties of Diamond
Authors: Miskovsky N. M. , Cutler P. H. , Huang Z.-H. , D'Ambrosio P. , Lerner P. 
Published: April 2011

ABSTRACTElectron field emission from diamond films was calculated using a model consisting of the projection of the energy-band surfaces in the <111>, <110> and <100> emission directions. It is found that the tunneling from bulk conduction and valance bands is negligible in p-type diamond, while emission from n-type doped diamond, surface states located near the conduction band edge, and hypothesized defect bands in the energy gap all have sufficient transmission probabilities to produce the low power-high current observed in experiments. To understand the mechanism for supplying electrons to these tunneling states, we analyze charge transport in diamond with internal fields. In particular, a Monte Carlo simulation was performed for electrons in the conduction band as a function of field and film thickness. The results predict hot electron behavior at lower fields with a transition to ballistic-like behavior for high fields (≥ 10 V/μm) and thin samples (≤0.1 μm). It is suggested that if a viable electron injection mechanism into the conduction band of a diamond-metal or diamond-semiconductor interface could be found for those faces of diamond exhibiting NEA, then a copious cold cathode electron emitter with field tunable energies is feasible.
Homoepitaxial Mosaic Growth and Liftoff of Diamond Films
Authors: Pehrsson Pehr E. , Mccormick Terri , Alexander W. Brock , Marchywka Mike , Black David , Butler James E. , Prawer Steven 
Published: April 2011

ABSTRACTGrowth of large area, single or almost single crystal diamond is of great importance to the electronics industry. In this work, single crystal diamonds were implanted with C+ ions, inducing a subsurface damage layer in the diamond lattice. Homoepitiaxial diamond films were then grown on the implanted crystals using a microwave plasma CVD reactor. Films grown on on-axis substrates were dominated by large numbers of hillocks, renucleation and penetration twins, while miscut substrates exhibited stepflow growth. The homoepitaxial layers were separated from the substrate by a water-based etch which selectively attacks the subsurface damage layer of the diamond lattice. The films were analyzed by Raman scattering, scanning electron microscopy (SEM), optical microscopy, photo- and cathodoluminescence, and x-ray diffraction. CVD growth on adjacent, oriented substrates formed a single, continuous diamond layer. The resulting homoepitaxial film quality, orientation, defect density and it's relationship to the underlying substrates were compared at various points on the surface, particularly the region which overgrew the gap between different substrates.
Defects and Morphology of Homoepitaxial Diamond Films on Natural Nonplanar and Isotopically Pure Planar Substrates
Authors: McCauley Thomas S. , Vohra Yogesh K. 
Published: April 2011

ABSTRACTWe have carried out diamond deposition by microwave plasma-assisted chemical vapor deposition (MPCVD) on planar and nonplanar diamond substrates at temperatures between 850° and 2000° C. The nonplanar and planar substrates were the polished (100) surfaces of type Ia natural diamond anvils and isotopically pure (99.95% 12C) type Ila synthetic crystals, respectively. The extremely low level of lattice and optical defects in the isopure substrates relative to natural crystals makes them ideal for optical characterization and defect studies, as well as high performance optical and electronic applications [1's (1) geometry, (2) type (defect density), and (3) temperature. The phase purity and defect structure of the films were analyzed by micro-Raman and low temperature photoluminescence (PL) spectroscopy. Optical and atomic force microscopy (AFM) were used to examine the surface morphology of the films. High temperature growth on the nonplanar anvil tip was anisotropic and extremely rapid (50-400 μm/hr), with significant incorporation of optically active defects. A possible model for the observed rapid growth is discussed. The films grown at lower temperatures on planar isopure substrates showed a dense array of oriented, stepped, square growth hillocks with penetration twins at their tops, while those grown at higher temperatures exhibited reasonably smooth, <110> oriented macrosteps. The higher temperature planar films showed a larger variety of incorporated optical centers than the lower temperature films.
Heteroepitaxial Nucleation of Diamond
Authors: Stoner B. R. , Ellis P. J. , Mcclure M. T. , Wolter S. D. 
Published: April 2011

ABSTRACTThe heteroepitaxial nucleation and eventual growth of large area single crystal diamond films has long eluded researchers interested in tapping it's many enabling properties, specifically in the field of active electronics. The uncertainty surrounding the diamond nucleation mechanism(s) and corresponding inability to carefully control this process are often blamed for the difficulty in achieving true heteroepitaxial growth. Biasenhanced nucleation (BEN) has been shown to provide in-situ control of the nucleation process. Subsequent advancements in both nucleation and deposition stages has resulted in highly oriented diamond films, approaching single crystal quality yet still plagued by arrays of medium to low angle grain boundaries that can degrade the electronic transport properties. To further improve upon these results and achieve large area, single crystal films it is believed that development must focus on the more fundamental problems of diamond nucleation. This paper presents a review of recent progress pertaining to the bias-enhanced process and focuses on data specific to the epitaxial nucleation dilemma.
Free Radicals from Photolysis of (NTO) 5-Nitro-2,4-Dihydro-3H-1,2,4-Triazol-3-One Studied by EPR Spin Trapping
Authors: Pace M. D. , Fan L. , Burkey T. 
Published: April 2011

AbstractNTO (5-Nitro-2,4-dihydro-3H-1,2,4-triazol-3-one)is shown to form aphotochemical free radical in alkaline aqueous solution containing nitromethane (CH3NO2). The NTO free radical can also be produced by chemical reduction of NTO with hydroquinone in alkaline solution. Details of radical formation and assignment of the NTO radical to a nitro anion radical, having the NTO ring intact, are presented.
Effect of Structure of Energetic Materials on Burning Rate
Authors: Fogelzang A. E. , Sinditskii V. P. , Egorshev V. Y. , Serushkin V. V. 
Published: April 2011

AbstractData on the steady-state combustion in a constant-pressure bomb at 0.1–40 MPa are presented for energetic materials from the following classes: metal salts of organic explosive acids, salts of organic bases with inorganic oxidizing acids, explosive coordination compounds, and endothermic polynitrogen compounds.For combustion of salts of organic bases with oxidizing acids it has been found that an increase in the oxidant redox potential, whose value serves as an estimate of the oxidizer reactivity, causes the burning rate value to increase. The same tendency has been disclosed for explosive coordination compounds which can formally be considered as metal-containing analogs of the salts of organic bases with oxidizing acids.The introduction of a metal atom in an organic explosive acid has been shown to result generally in an enhancement of the burning rate, with the effectiveness of the metal as the combustion catalyst being dependent not only on the nature of the metal but on its position in the molecule as well.Neither the nature of the metal, nor the nature and structure of the ligand really affects the combustion of coordination compounds of metal azides, whose combustion occurs at the expense of the heat produced in the decomposition process. All the coordination azides seem to have the same rate-limiting stage, namely, the decomposition of the intermediate HN3 and differ from one another by their burning temperatures. The similar behavior is also characteristic of metalless analogs of the coordination azides: salts of HN3 with amines.
Toward Quantitative Thermodynamics and Kinetics of Pyrolysis of Bulk Materials at High Temperature and Pressure
Authors: Williams G. K. , Brill T. B. 
Published: April 2011

AbstractAn evaluation was made of whether T-jump/FTIR spectroscopy could be used to determine the decomposition kinetics (Ea and ln A) and thermochemical (ΔHd) constants of an energetic material at high temperature and high heating rate. Polystyrene peroxide was chosen because of its known, simple, decomposition process. The kinetic constants are reasonable for O-O bond homolysis as the rate determining step: Ea = 39 kcal/mol, ln (A, s−1 ) = 21.5. Significant uncertainty exists, however, in the estimation of ΔHd.
Self-Affinity of Combustion-Generated Aggregates
Authors: Neimark A. V. , Köylü Ü. Ö. , Rosner D. E. 
Published: April 2011

AbstractA large population of combustion-generated soot aggregates (more than 3,000 samples) was thermophoretically extracted from a variety of laminar and turbulent flames and analyzed using transmission electron microscopy (TEM). It was shown that the scaling structural properties of these fractal aggregates cannot be exclusively characterized by a single mass fractal dimension. Asymmetric properties of the aggregates were considered here by first assuming and then demonstrating their self-affinity via. an affinity exponent reflecting scaling with respect to the length and width of the aggregate projections. In addition to the conventional fractal dimension, Df, determined by using the geometrical mean of the longitudinal and transverse sizes as the characteristic length, the affinity exponent, H, and two complementary fractal dimensions, one longitudinal, DL =[(1+H)/2 ]Df, and one transverse, DW =[(1+H)/2H]Df, were introduced. By fitting TEM data for the entire population of aggregates, the values Df = 1.75 and H = 0.91 were obtained. This more complete description of aggregate morphologies in terms of the self-affine scaling is expected to lead to a better understanding of the transport properties and restructuring kinetics of flame-generated aggregates.
Nitric Oxide Interactions with C2 Hydrocarbon Species
Authors: Williams B. A. , Pasternack L. 
Published: April 2011

AbstractWe have investigated the combustion chemistry of nitric oxide doped into premixed 10 Torr flames of CH4/O2/N2, C2H6/O2/N2, C2H2/O2/N2, and C2H2O2N2 which had similar peak temperatures. Profiles of OH, CH, 3C2, CN, NCO, NH, and NO were recorded by laser-induced fluorescence and compared among the different fuels, indicating differences in hydrocarbon flame structure and NO reactivity in these environments. Concentrations of nitrogen intermediates are comparable for the methane, ethane, and ethylene flames, but are approximately a factor of three higher with acetylene, indicating much greater NO reactivity in this flame.
Products and Kinetics of Flash Pyrolysis of Peg: A Minimum Smoke Binder
Authors: Arisawa H. , Brill T. B. 
Published: April 2011

AbstractFlash pyrolysis of polyethyleneglycol by T-Jump/FTIR spectroscopy to temperatures of the surface during combustion reveals that volatile products arise from approximately equal amounts of C-O and C-C homolysis. Nine volatile products are discussed. The average number of repeating units in the volatile oligomers is 2.5. A shift in product distribution occurs at 420–480°C resulting from a change in the polymer structure. Below 420°C, di- and mono-ether oligomers and diethyleneglycol dominate. Above 480°C, the mono-ethers and ethyleneglycol dominate. The Arrhenius constants for decomposition reflect this difference: Ea=8.8 kcal mol−1, In (A, s−1) =2.0 at 370–420°C and Ea=19 kcal mol−1, In (A, s−1)=10 at 480–550°C.
Combustion Chemistry of Energetic Materials Studied by Probing Mass Spectrometry
Authors: Korobeinichev O. P. , Kuibida L. V. , Paletsky A. A. , Shmakov A. G. 
Published: April 2011

AbstractThe methods of probing mass spectrometry (PMS) for diagnostic of flames and for the study of kinetics and mechanism of the thermal decomposition products of energetic materials (EM) are described. Several types of instruments based on microprobe and molecular beam mass spectrometric sampling have been developed. Time of flight mass spectrometer has been used. Apparatuses for high (10 atm) and low (<1 atm) pressure have been developed for the study of combustion and decomposition of EM by PMS “in situ”. Several examples are presented to demonstrate application of PMS method for the study of EM flame structure, thermal decomposition and dynamic of ignition. Experimental data on decomposition of double base propellants ammonium dinitramide, ammonium perchlorate are presented.
Effects of Nanoscale Voids on the Sensitivity of Model Energetic Materials
Authors: Whitea C. T , Barretta J. J. C. , Mintmirea J. W. , Elert M. L. , Robertson D. H. 
Published: April 2011

AbstractBecause of its importance in designing safer, more reliable explosives the shock to detonation transition in condensed phase energetic materials has long been a subject of experimental and theoretical study. This transition is thought to involve local hot-spots which represent regions in the material which couple efficiently to the shock wave leading to a locally higher temperature and ultimately initiation. However, how at the atomic scale energy is transferred from the shock front into these local “hot spots” remains a key question to be answered in studies of the predetonation process. In this paper we report results of molecular dynamics simulations that suggest that even nanometer scale defects can play an important role in the shock to detonation transition.
Molecular Dynamics Study of the Effect of Varying Exothermicity on the Properties of Condensed-Phase Detonation
Authors: Elert M. L. , Robertson D. H. , White C. T. 
Published: April 2011

AbstractTo investigate the role of exothermicity on the properties of a chemically sustained shock waves, a series of two-dimensional molecular dynamics simulations was carried out in which the exothermicity was systematically varied. The simulations were based on a model diatomic system which has been previously shown to produce reasonable values for shock wave properties. A decrease of 33% in the amount of energy released in the reaction produced a significant decrease in detonation front velocity and an increase in the impact energy necessary to initiate a sustained shock wave. Redistribution of energy between the reaction products at constant total exothermicity had a much smaller effect on the properties of the detonation front.
Ultrafast Dynamics of Shock Waves and Shocked Energetic Materials
Authors: Hare David E. , Lee I-Y. Sandy , Hill Jeffrey R. , Franken Jens , Suzuki Honoh , Baer Bruce J. , Chronister Eric L. , Dlott Dana D 
Published: April 2011

AbstractExperimental measurements of material effects induced by the passage of sharp shock fronts require techniques which provide high temporal resolution and high spatial resolution. Since typical shock velocities are a few microns per nanosecond, sub-nanosecond probing requires sub-micron spatial resolution. In our experiments, the required temporal resolution is furnished using picosecond laser generated shock waves and picosecond spectroscopy. The spatial resolution is furnished by engineering nanometer scale structures into our shock target arrays. In one technique, absorption transients in the spectrum of a thin layer of molecules, termed an optical nanogauge, are investigated. Shock-induced molecular energy transfer processes are observed in condensed matter for the first time. In a second technique, sub-micron particles of an energetic material are shocked and probed using ps coherent Raman spectroscopy. This probing technique permits the instantaneous measurement of the temperature, pressure and composition of an energetic material under dynamic shock loading.
Heterogeneous Reaction of Boron in CHNO and CHNOF Environments Using High-Pressure Matrix Isolation
Authors: Rice Jane K. , Russell Thomas P. 
Published: April 2011

AbstractWe have developed a technique in which the decomposition of energetic materials can be initiated under high pressure conditions which resemble the pressures reached in the non-ideal detonation process. A gem anvil cell is cooled to cryogenic temperatures, 50 K, and remains in thermal contact with the cooling element throughout the experiment. Following initiation, the reaction products are rapidly cooled and quenched on the microsecond time scale and detected using FTIR spectroscopy. In the present study, binary mixtures of boron with energetic materials containing (CHNOF) and lacking fluorine (CHNO) are compared. The differences in the reaction products suggest that the presence of the fluorine substituent leads to a complete combustion of boron to B2O3. In the decomposition of binary mixtures lacking the fluorine substituent, the boron in appears to be unchanged following the reaction of the oxidizer. The observed products are compared to predict the affect of fluorine on the formation of boron combustion products in the two environments.