bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature Sensor On Boron Ion Implanted Diamond
Authors: Job R. , Denisenko A. V. , Zaitsev A. M. , Werner M. , Melnikov A. A. , Fahrner W. R. 
Published: April 2011

ABSTRACTp-type semiconducting boron doped layers have been fabricated on diamond substrates by ion implantation and subsequent annealing. A number of the related published experimental data and theoretical models on electrical properties of boron doped diamond are analyzed with regard to the temperature coefficient of resistance (TCR) of temperature sensors. The dependencies of the conductivity and activation energy on three parameters: (i) boron doping level NA, (ii) electrical compensation ratio ND/NA- C and (iii) duration of the postimplantation annealing time ta are studied. By variation of NA, C and t, an optimized technological regime for the temperature sensor fabrication can be obtained. One can summarize that: 1) the TCR value is not remarkably reduced with the boron concentration up to NA -1019 cm-3, 2) an increase of the electrical compensation decreases the activation energy and consequently the TCR coefficient,3) 1 h annealing at 1500°C is sufficient to remove the compensating radiation defects, 4) the variation of the ta from 1 min to 1 h changes the TCR value by 20% to 30%. Technological steps of the fabrication of a micro temperature sensor are given.
Microstructures of Amorphic Diamond™ Films Deposited by Laser-Ablation
Authors: Sohn Hyunchul , Krishnan Kannan , Fink Richard 
Published: April 2011

ABSTRACTMicrostructures of Amorphic Diamond™ films deposited by laser ablation method were investigated using transmission electron microscopy. The AD films matrix was homogeneous with a sp3-type bonding fraction of 40%∼45% confirmed by electron energy-loss spectroscopy. The sp3 bonding fraction decreased monotonically with increasing annealing temperature. The main inhomogeneity in Amorphic Diamond™ was observed to be particulates of high density (>105/cm2) distributed through the depth of the film. Particulate size ranged from ∼10nm to a few μm and most of them were identified to be graphite. Large particles (>0.5μm) were agglomerates of smaller graphite crystallites. Possible mechanisms for cold field emission are discussed based on the microstructures observed in these AD films.
Studies of Pyrolysis Products of Explosives in Soils using Infrared Tunable Diode Laser Detection
Authors: Wormhoudt J. , Shorter J. H. , Kolb C. E. 
Published: April 2011

AbstractWe report on laboratory studies of the thermal decomposition of TNT under a variety of conditions. Our goal is a better understanding of the soil contamination detection technique used in site characterization using cone penetrometers, in which hot filament pyrolysis results in small gaseous molecules, such as NO, which can be detected by a variety of methods to indicate the presence of explosives in the soil. Our laboratory studies use a long-path sampling cell and tunable infrared diode laser absorption, which provide sensitive, specific, time-resolved detection of several of the key decomposition products. In this paper, we present both the initial results of laboratory experiments on mixtures of soil and TNT, designed to simulate the operation of a cone penetrometer probe, and also results of a series of heated tube experiments which serve to relate the first type of experiment to previously reported TNT decomposition studies.
The Design of Stable High Nitrogen Systems
Authors: Tartakovsky V. A. 
Published: April 2011

AbstractA general strategy for the design of high nitrogen systems with an adequate degree of stability has been elaborated. The design of nitro compounds in which terminal nitro groups are bonded to the chain of several heteroatoms is a specific case within the strategy. In the process of working out the strategy a number of new high nitrogen systems ( dinitrazenic acid or dinitroamide HN3O4 and it salts, nitrodiazene oxides RN3O3 and tetrazine dioxides ) were discovered.A number of new types of nitro compounds (bicyclo nitro-bis-hydroxylamine, nitrohydrazine, nitrohydroxylamine, sulfo-N-nitroimide and bis-N-nitroimide were synthesized.This study opens new prospects in the field of the synthesis of high energy materials.
New Energetic Epoxy Binders
Authors: Jain S. R. , Amanulla S. 
Published: April 2011

AbstractA new class of epoxy resins having N-N bonds in the backbone has been synthesized with a view to explore their properties as energetic binders. The N-epoxidation of bis-dicarbonylhydrazones of adipic, azelaic and sebacic dihydrazides results in the formation of viscous resins having epoxide end groups. The resins have been characterized by the elemental and end group analyses, IR and NMR spectra. Relevant properties for their use as binders in solid propellants, such as thermal stability, heat of combustion, burn rate and performance parameters of AP-based propellant systems, have been evaluated. A significant increase in the burn rate of AP-based propellants noticed, is perhaps related to the exothermicity of the binder decomposition and the reactivity of N-N bonds with perchloric acid formed during the combustion of AP.
Polynitroalkanes, Nitroazoles and Oximes in Electroorganic Synthesis
Authors: Niyazymbetov Murat 
Published: April 2011

AbstractElectrochemical oxidation of anions of polynitroalkanes (PNA) proceeds via one-electron transfer and results in the formation of unstable radicals. The radicals undergo fragmentation, abstraction of a hydrogen atom from the solvent, and reaction with aromatic compounds to form aryl-PNA. The yield of aryl-PNA depends on the structure of the radicals and on the electron donating properties of the aromatic substrates. Due to their electrophilic properties, PNA-radicals also react with compounds containing heteroatoms with unshared electron pairs resulting in formation of dinitromethylides. Under anodic electrolysis conditions dinitromethylides which have a carbanionic structure can effectively transfer the dinitromethyl group to other organic substrates. Electrochemical oxidation of anions of nitroazoles also proceeds via one-electron transfer to generate nitroazolyl radicals. Their principal reaction is abstraction of hydrogen from the solvent. However, electrolysis of nitroazoles in the presence of aromatic compounds results in formation of N-aryl derivatives in good yield. It has been shown that electrooxidation of mono oximes leads to formation of unstable nitroso dimers, while electrooxidation of vicinal dioximes results in formation of furoxans in high yield.
Time Resolved Optical Spectroscopy to Examine Chemical Decomposition of Energetic Materials Under Static High Pressure and Pulsed Heating Conditions
Authors: Russell Thomas P. , Allen Theresa M. , Gupta Y. M. 
Published: April 2011

AbstractThe study of the deflagration or detonation reactions of energetic materials is challenging due to the high pressure, high temperature, and time domain under which the reactions occur. Experimental measurements, are presented that demonstrate the ability to continuously monitor the global reaction times and reaction sequences associated with chemical reactions under these conditions. Time resolved absorption spectroscopy is used in conjunction with a high pressure gem anvil cell to probe the real-time chemical processes during pulsed-heating. Samples are initiated by a rapid thermal jump induced by absorption of a single laser pulse. Time resolved absorption spectroscopy of 3,6 trinitroethylamine tetrazine reaction is demonstrated by the real time measurement of the decrease in the ϕ-ϕ* absorption at 110 ns temporal resolution during laser heating at pressures up to 3.5 Gpa
A Reactive Flow Model with Coupled Reaction Kinetics for Detonation and Combustion in Non-Ideal Explosives
Authors: Miller Philip J. 
Published: April 2011

AbstractA new reactive flow model for highly non-ideal explosives and propellants is presented. These compostions, which contain large amounts of metal, upon explosion have reaction kinetics that are characteristic of both fast detonation and slow metal combustion chemistry. A reaction model for these systems was incorporated into the two-dimensional, finite element, Lagrangian hydrodynamic code, DYNA2D. A description of how to determine the model parameters is given.
Anta and its Oxidation Products
Authors: Lee Kien-Yin , Gilardi Richard , Hiskey Michael A. , Stine James R. 
Published: April 2011

Abstract5-Amino-3-nitro-lH-1,2,4-triazole (ANTA) is a molecule with high stability. Aside from being an insensitive high explosive (IHE), it is also used as a synthon for other potential new IHEs. The crystal structure of ANTA was resolved by X-ray crystallography. However, when ANTA was recrystallized from 2-butanone, crystals with molecular packing characterized by extended planar sheets were obtained (ß-ANTA). The crystal density of ß-ANTA is 1.73 g/cm3, which is less dense than α-ANTA (p = 1.82g/cm3).The high-nitrogen molecule, 5,5'-dinitro-3,3'-azo-1,2,4-triazole (DNAT) was calculated to have a high density and a positive heat of formation (AHf). In an attempt to prepare DNAT, we have studied the oxidation of ANTA with different oxidizers. It was found that DNAT is the reaction product when the potassium salt of ANTA was oxidized with potassium permanganate. However, when ANTA was oxidized with ammonium persulfate in aqueous medium, one of the reaction products obtained was the azoxy moleclue of DNAT (DNAzT). We are unable to determine the crystal densities of either DNAT and DNAzT because the crystals obtained were solvated with the crystallization solvents.
Fast Color Detection with Two-Terminal P-I-I-N Devices
Authors: Neidlinger T. , Schubert M. B. , Schmid G. , Brummack H. 
Published: April 2011

AbstractIn order to overcome the intrinsic speed limitation of amorphous silicon nipin color sensors we present an alternative way of achieving bias-controlled spectral sensitivity of two-terminal thin film devices, piin structures with appropriate band gap and thickness of their single layers can be used as photodetectors that are able to sequentially extract different color signals. Color separation is achieved by controlling the absorption and electric field profile across these piin devices, and thanks to the differences in electron and hole transport properties. Because in contrast to nipin devices there is no need for reverting readout voltages for color separation, this type of sensors can be operated at much higher readout frequencies. Spectral response and bias voltage transients have been analysed up to 20kHz, and preliminiary data are presented on the optimization of speed, dynamic range and color separation by varying bandgap and thickness of p- and i-layers. Furthermore a three-color sensor has been realized by introducing an additional intrinsic layer.
Capacitance Characterization of Amorphous Silicon/Amorphous Silicon Germanium Heterostructures
Authors: Palsule C. , Paschen U. , Cohen J. D. , Yang J. , Guha S. 
Published: April 2011

AbstractWe have performed voltage-pulse stimulated capacitance transient measurements along with other junction capacitance measurements on a-Si:H/ a-Si,Ge:H heterostructures deposited on p-type crystalline silicon using the glow discharge technique. For a filling pulse that puts the c-Si/a-Si:H junction in forward bias, the capacitance transients consist of two components- a fast component corresponding to electron emission and a slow component corresponding to hole emission. For a fixed starting reverse bias, we have found that the density of trapped holes is proportional to the product of the filling pulse voltage and the filling pulse width and reaches a saturation value at a certain value of the product. These hole traps appear to reside at or very close to the a-Si:H/a-Si,Ge:H interface. The estimated trap concentration is around 1011/cm2 and is independent of temperature and applied bias, ruling out the creation of the traps during the filling pulse. We also report results on samples in which a-Si:H/ a-Si,Ge:H interface has been modified during growth to alter the concentration of the hole traps.
Admittance of a-Si:H/c-Si Schottky Diodes
Authors: Gall S. , Hirschauer R. , Kolter M. , Bräunig D. 
Published: April 2011

AbstractWe have measured the admittance (conductance and capacitance) of a-Si:H/c-Si heterostructure Schottky diodes as a function of frequency, temperature and voltage in the dark and under spectral illumination (in the wavelength range between λ=500nm and λ=1200nm). Thus, it is possible to observe the activation/deactivation of trapping-detrapping effects within the a-Si:H layer (near the a-Si:H/c-Si interface). We have determined the conduction band offset of the a-Si:H/c-Si heterostructure. The spectral behaviour of the admittance is dominated by the absorption of light in the c-Si and the valence band offset of the heterojunction. We have also developed an equivalent circuit of the a-Si:H/c-Si heterostructure Schottky diode in the dark, which is capable of describing the measured behaviour.
Physics of Below Threshold Current Distribution in a-Si:H TFTs
Authors: Slade H. C. , Shur M. S. , Deane S. C. , Hack M. 
Published: April 2011

AbstractWe have examined the material properties and operation of bottom-gate amorphous silicon thin film transistors (TFTs) using temperature measurements of the subthreshold current. From the derivative of current activation energy with respect to gate bias, we have deduced information about the density of states for several different transistor types. We have demonstrated that, in TFTs with thin active layers and top nitride passivation, the current conduction channel moves from the gate insulator interface to the passivation insulator interface as the transistor switches off. Our 2D simulations clarify these experimental results. We have examined the effect of bias stress on the transistors and analyzed the resulting reduction in the subthreshold slope. Based on these results, we have extended our analytic amorphous silicon TFT SPICE model to include the effect of bias stress.
Material Basis of Highly Stable a-Si:H Solar Cells
Authors: Rech B. , Wieder S. , Siebke F. , Beneking C. , Wagner H. 
Published: April 2011

AbstractWe achieved a stabilized efficiency of 9.2 % after only 8 % relative degradation for an a-Si:H/a-Si:H stacked cell with the top-cell i-layer prepared at 140 °C using a high hydrogen dilution of the silane process gas. From a comprehensive characterization of p-i-n cells and the corresponding i-layer material prepared at 140 °C and 190 °C substrate temperature with different hydrogen dilutions, we conclude that the performance of these pin cells strongly correlates with the material properties of the corresponding i-layers. High fill factors after light soaking are reflected in a good microstructure, high photo-conductivity, and relatively low defect density. Whereas the initial Voc is limited by interface recombination, volume recombination dominates the forward-dark current after light soaking. The stabilized Voc as well as the short-circuit current densities correlate with the optical bandgap of the i-layer.
High-Rate Rpecvd of a-Si:H Films by Means of a VHF Resonant Plasma Source
Authors: Blum T. , Suchaneck G. , Kuske J. , Stephan U. , Beyer W. , Kottwitz A. 
Published: April 2011

AbstractHigh deposition rate (up to 5 nm/s) a-Si:H films suitable for recrystallization were deposited using a λ/4 helical resonator source. Refractive index, Tauc-gap, photo- and dark conductivities were measured for film characterization. The metastable behaviour was characterized by the light- induced degradation of the photoconductivity. Hydrogen content and bonding configuration were analyzed by IR absorption and mass separated thermal effusion transients, film microstructure was studied by intentionally incorporating carbon and oxygen. Most of the hydrogen is located on internal surfaces in the otherwise dense material. Differences between the deposition from our highly excited plasma and the conventional remote PECVD process are discussed.
Investigation of the Amorphous to Nanocrystalline Phase Transition at the Deposition of Silicon Films in an ECWR Plasma of Pure SiH4
Authors: Scheib M. , Schrcder B. , Oechsner H. 
Published: April 2011

AbstractA novel plasma based chemical vapour deposition (PECVD) technique employing electron cyclotron wave resonance (ECWR) for plasma excitation was applied to the deposition of hydrogenated nanocrystalline silicon (nc-Si:H) films. nc-Si:H films were produced at deposition rates up to 8Å/sec (TS = 200°C) with a pure SiH4 plasma in contrast to the conventional glow discharge technique where the high hydrogen dilution usually needed leads to considerable lower deposition rates. The amorphous-to-nanocrystalline phase transition was investigated in dependence of substrate temperature, the hf-power and magnetic field mandatory for ECWR, and SiH4-flow into the plasma. With the knowledge of the plasma parameters derived from single probe measurements, and the intensities of excited plasma species detected by means of optical emission spectroscopy we can qualitatively describe the silane-plasma dissociation behaviour. The nanocrystalline phase is found to be always deposited when the dissociation degree of the SiH4 plasma is almost saturated.
Trap Dominated Hydrogen Transport in Disordered Silicon
Authors: Nickel N. H. , Jackson W. B. , Walker J. 
Published: April 2011

AbstractHydrogen transport in polycrystalline silicon was investigated by deuterium diffusion experiments. D was introduced either from a remote plasma or a solid-state source. The data can be explained by a two-level model used to explain diffusion in amorphous silicon. The energy difference between transport level and deuterium chemical potential was found to be 1.3 eV. A band of shallow levels for hydrogen trapping is located about 0.6 eV below the transport level, while deep levels are about 1.7 eV below.
Metastable Defects in a-Si:H from Bond-length Disorder
Authors: li Qiming , Biswas R. 
Published: April 2011

AbstractA model of metastable defect formation via H-rebonding in hydrogenated amorphous silicon is developed where the defect density and defect formation energy are controlled by the bond-length disorder of the material. Dangling bond defects are created by H motion from SiH bonds to weak Si-Si bonds. The model predicts formation energies for thermal and light-induced defects in good agreement with experiment. The relaxation of thermal equilibrium defects is stretched exponential, with stretch parameters varying approximately linearly with temperature and relaxation times that are thermally activated- in good agreement with experiment. The annealing of light-induced defect densities also shows relaxation behavior. The model accounts for barriers of ≈ 1.5 eV for H diffusion. The energetics of the H*2 complex will also be discussed. The rms bond-length deviation is a new parameter that controls the quality of the material.
The Density-of-States Concept Versus the Experimentally Determined Distribution of Activation Energies
Authors: Adriaenssens Guy J. , Arkhipov Vladimir I. 
Published: April 2011

AbstractRandom fluctuations of localized state energies will result in thermal release of carriers trapped in those states at shorter times than would be observed from a stationary distribution of the same energies. An experimentally observed distribution of activation energies will hence differ from the distribution of average energies of the states involved. It will also be temperature-dependent. In a-Si:H, low-frequency fluctuations with a spectrum comparable to the one of 1/f noise, can account for the measured temperature dependence of the distribution. They also explain the apparent shift in localized-state energy under steady-state illumination.
Structural Evolution of Top-Junction a-Si:C:H:B and Mixed-Phase (Microcrystalline Si)-(a-Sil-xCx:H) p-Layers in a-Si:H n-i-p Solar Cells
Authors: Koh Joohyun , Burnham J. S. , Li Yeeheng , Liu Hongyue , Chen Ing-Shin , Pilione L. J. , Wronski C. R. , Collins R. W. 
Published: April 2011

AbstractWe have applied real time spectroellipsometry (RTSE) to study hydrogenated amorphous silicon (a-Si:H) solar cells fabricated in the Cr/n-i-p configuration using plasma-enhanced chemical vapor deposition (PECVD) in a single-chamber system. The microstructural evolution of the n-, i-, and p-layers of the devices has been determined, including the thicknesses of the bulk, interface, and surface roughness layers versus time. The optical properties of the individual layers, including the dielectric functions and optical gaps, have also been obtained in the same analysis. In this study, we have focused on i/p interface formation and, in particular, on the nucleation process for differently-prepared a-Si:C:H and mixed-phase μc-Si:H/a-Si1-xCx:H p-layers on the a-Si:H i-layer. From the thickness dependence of the p-layer void volume fraction, we can obtain an estimate of the thickness at which nuclei make contact to form a continuous film. For the mixed-phase p-layers, the nuclei contact thickness can be reduced by exposing the i-layer to a H2-plasma prior to p-layer deposition. We have found that for similarly-prepared p-layers this reduction in contact thickness leads to an increase in open-circuit voltage of the solar cell
Light Bias CPM Study of the Density of States in N-type Amorphous Silicon
Authors: Unold Thomas , Branz Howard M. , Vanecek Milan 
Published: April 2011

AbstractWe measure subgap absorption on n-type amorphous silicon using the “absolute” constant photocurrent method. We find that for typical monochromator probe beam intensities the measurement is not significantly influenced by lifetime changes. When the measurement is performed under light bias, an apparent increase in the defect absorption coefficient is observed, but no change in the photoexcitation threshold or spectral shape of the absorption band is seen. We show that this increase is likely due to a bias-light amplification of spectrally dependent lifetime changes. Our measurements suggest a larger electron capture cross section of positive valence band tail states compared to neutral dangling bonds.
Low Frequency Noise Behavior in a-Si:H Schottky Barrier Devices
Authors: Aflatooni K. , Nathan A. , Hornsey R. 
Published: April 2011

AbstractWe present a systematic experimental study of low frequency noise behavior in Mo/a-Si:H Schottky diodes under reverse bias operation. The noise in the Schottky diode was found to increase with increasing reverse current and with an approximate 1/f behavior at low bias voltages, yielding a Hooge parameter in the range (2 to 3) × 10−4. At high reverse voltages, due to electrical stressing and hence, bias-induced material instability, a significant deviation from the 1/f behavior was observed.
Time-Resolved Photoluminescence in a-Si1-xCx:H
Authors: Tessler Leandro R. , Cirino Lucicleide R. 
Published: April 2011

AbstractThe dependence of the photoluminescence (PL) decay on temperature and composition of a series of amorphous silicon-carbon alloys (a-Si1-xCx:H) with 0 <x <0.4 was studied. The samples were prepared by “low power” PECVD from SiH4/CH4 gas mixtures. The decay curves are non-exponential and can be described as lifetime distributions (LTD). For pure a-Si:H at 17 K the peak of the LTD is of the order of 5×10-4 sec. It shifts to shorter lifetimes as x or the temperature increases. Samples with x > 0.3 present in addition a faster peak with maximum at 10-8 sec. The fast peak is almost temperature independent. The slow component shifts to shorter lifetimes as the temperature increases, and vanishes at room temperature. The presence of the fast peak is interpreted as due to a change in the radiative recombination mechanism. We associate this peak to the recombination of trapped “excitons”.