bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Composition, Structure, and Sensitivity of Explosives
Authors: Storm Carlyle B. , Travis James R.
Published: March 2011

High explosives, blasting agents, propellants, and pyrotechnics are all metastable relative to reaction products and are termed energetic materials. They are thermodynamically unstable but the kinetics of decomposition at ambient conditions are sufficiently slow that they can be handled safely under controlled conditions. The ease with which an energetic material can be caused to undergo a violent reaction or detonation is called its sensitivity. Sensitivity tests for energetic materials are aimed at defining the response of the material to a specific situation, usually prompt shock initiation or a delayed reaction in an accident. The observed response is always due to a combination of the physical state and the molecular structure of the material. Modeling of any initiation process must consider both factors. The physical state of the material determines how and where the energy is deposited in the material. The molecular structure in the solid state determines the mechanism of decomposition of the material and the rate of energy release. Slower inherent reaction chemistry leads to longer reaction zones in detonation and inherently safer materials. Slower chemistry also requires hot spots involved in initiation to be hotter and to survive for longer periods of time. High thermal conductivity also leads to quenching of small hot spots and makes a material more difficult to initiate. Early endothermic decomposition chemistry also delays initiation by delaying heat release to support hot spot growth. The growth to violent reaction or detonation also depends on the nature of the early reaction products. If chemical intermediates are produced that drive further accelerating autocatalytic decomposition the initiation will grow rapidly to a violent reaction.
Surface Chemistry of Energetic Materials at High Temperature
Authors: Brill Thomas B.
Published: March 2011

The chemistry at the surface of a burning propellant plays a major role in the burnrate, the stability of the flame, and the potential for a run-away hazardous event. Chemical details can be determined experimentally by simulating the burning surface with a thin film of material heated rapidly to the surface temperature. T-Jump/FTIR spectroscopy is designed to create these conditions. The dominant, initial, heat-producing reactions in the surface zone of NH4ClO4, NH4NO3, NH4[N(NO2)2], HMX, RDX, and DNNC are elucidated at high temperatures representative of the burning surface.
Correlation Time for Polymer Chain Motion Near the Glass Transition in Nitrocellulose.
Authors: Jayakody J. R. P. , Bulusu S. , Marino R. A.
Published: March 2011

The NMR chemical shift anisotropy (CSA) has a temperature dependence as a result of thermal motions of the NMR site. For slow motions of a polymer chain at or near the glass transition, Tg, the CSA begins to decrease, with the characteristic powder pattern features, shoulders and divergence, approaching one another. This motional narrowing can be interpreted to yield the correlation time of the thermal motions. If Δ is the rigid-lattice shoulder to shoulder chemical shift anisotropy and τ is the correlation time of the slowmotion of the polymer chains, the total fractional shift, δ/Δ, for the general asymmetric case is found to be

derived using Lee's theory. In this work, Nitrocellulose isotopically highly enriched with 15N was studied at four temperatures between 27° and 120° Celsius. To circumvent signal-to-noise problems in obtaining CSA data from a polycrystalline/amorphous sample, we used the Magic Angle Spinning (MAS) technique of Herzfeld and Berger. The principal values of the chemical shift tensor were then obtained from the relative intensities of the spinning sidebands in the MAS NMR spectrum. Correlation times were found to be of the order of 400 ms at 70°C, and 17 ms at 120°C.
Laser-Based Sensitive Detection of Energetic Materials
Authors: Lemire G. W. , Simeonsson J. B. , Sausa R. C.
Published: March 2011

The development of a novel technique for sensing trace vapors of -NO2 containing compounds is reported. This technique is based on the use of one laser operating at 226 nm to both photofragment the target molecule and detect the characteristic NO fragment, formed from a rapid predissociation of NO2, by resonance-enhanced multiphoton ionization (REMPI) via its A2Σ+ - X2Π (0,0) band origin. The analytical utility of this technique is demonstrated on a number of compounds, including dimethylnitramine, nitromethane, nitrobenzene, TNT, and RDX, employing molecular beam sampling with time-of-flight mass spectrometric analysis of the jet cooled analyte seeded in an atmosphere of buffer gas. For RDX and TNT, a detection limit of 8 and 24 ppb, respectively, is demonstrated using a laser energy of 100 microjoules/pulse.
Nitrogen Radicals from Thermal and Photochemical Decomposition of Ammonium Perchlorate, Ammonium Dinitramide, and Cyclic Nitramines
Authors: Pace M. D.
Published: March 2011

Free-radical thermal and photochemical decomposition products of ammonium dinitramide (ADN), an acyclic nitramine, are compared to that of cyclic nitramines (RDX, HMX, and HNIW) and to ammonium perchlorate (AP). Photochemical formation of NO2 from uvphotolysis of ADN at 77 K is found to follow first-order kinetics; whereas, zero-order NO2 formation is observed from the cyclic nitramines under the conditions of this experiment. Mechanisms are suggested for ADN decomposition. A general trend of cyclic nitramines to thermally decompose forming nitroxide radicals is supported by 15N-ring-labeled HNIW results. ADN thermally decomposes at 19° C to form free-radical reaction products in solution with tetrahydrothiophene-1,1-dioxide.
The Importance of Sterically Hindered Shear in Determining the Sensitivity of Explosive Crystals
Authors: Dick Jerry J.
Published: March 2011

Sterically hindered shear in a plane shock wave in an explosive crystal is shown to be important in determining the shock sensitivity of pentaerythritol tetranitrate and nitromethane. The steric hindrance is analyzed at the intermolecular level in the unit cell, and compared to the experimental evidence.
Fracture Surface Topography of Octol Explosives
Authors: Lanzerotfi M. Yvonne D. , Pinto James J. , Wolfe Allan
Published: March 2011

Energetic materials are of significant interest for scientific and practical reasons in the extraction (mining) industry, space propulsion, and ordnance. The nature of the fracture process of such materials under high acceleration is of particular interest, especially in ordnance. This paper describes new experimental and analysis techniques that allow us to characterize quantitatively and to compare the fracture surfaces of different energetic materials, and to deduce the specific fracture mechanisms. The techniques are widely applicable to other composite systems. In the materials discussed herein, topographical profiles spaced 1.0 mm apart across the fracture surfaces of two types of Octol have been obtained with a diamond stylus profilometer. Spatial power spectra (wavelengths of 1.0 μm 1.0 cm) have been calculated using a prolate spheroidal data window in the horizontal space domain prior to using a fast Fourier transform algorithm. The spatial power density of the fracture surface profiles is found in general to decrease with increasing spatial frequency over the region of interest, ≈ 1 mm-1 to ≈ 1 cm-1. Quasi-periodic peaks corresponding to HMX particle sizes are observed in the Octol spatial power spectra. These peaks indicate the inhomogeneous HMX grain size distribution in the Octol fracture surfaces. Peaks in the Octol spectra indicate that intergranular fracture often occurs between the TNT and HMX grains. Fractal analysis of the Octol power spectral slopes indicates the regions of deterministic, intergranular failure and the regions of the nondeterministic, trans-granular failure through TNT or HMX grains. This non-deterministic (fractal) failure is chaotic and may indicate the origin of failure in the sample.
Characterization of SinGem Strained Layer Superlattice P-N Junctions
Authors: Engvall Jesper , Olajos Janos , Grimmeiss Hermann G. , Presting Hartmut , Kibbel Horst , Kasper Erich
Published: March 2011

A series of three p-n junctions consisting of ten monolayer strain adjusted SinGem superlattices (Si6Ge4, Si5Ge5, Si4Ge6) has been characterized with respect to Current-Voltage, Capacitance-Voltage and Short Circuit Photocurrent measurements. The samples were grown by MBE with an Antimony surfactant resulting in improved interface sharpness. Superlattice interband transitions were measured by Short Circuit Current spectroscopy and bandgap energies were determined by a fitting procedure. The temperature dependence of the junction capacitance and of the Short Circuit Current indicate a potential barrier for electrons at the superlattice-buffer interface that impedes electron transport from the p-n junction at lower temperatures.
The Relationship Between Surface Chemistry and Photoluminescence of Porous Silicon
Authors: Li Kun-Hsi , Tsai Chaochieh , Campbell Joe C. , Kovar Milan , White John M
Published: March 2011

Green photoluminescence (PL) is observed from an as-anodized porous Si wafer immersed in the anodization electrolyte and the PL turns red after the sample is removed from the electrolyte and is blown dry. The PL of porous Si immersed in alcohol exhibits a blue shift and a marked decrease in intensity relatively to dry, as-anodized wafers. However, when the immersed samples are treated with UV for a few minutes, the PL peak shifts to a longer wavelength. Fourier-transform infrared spectroscopy reveals that alkoxy surface species and silicon hydride species backbonded to oxygen atoms appear on the UV-treated samples. Furthermore, the PL characteristics and surface species of the UV-treated samples can be recovered to those of as-anodized wafers by dipping in HF. These results point out the importance of surface chemistry in the luminescence process of porous Si.
Enhanced Luminescence and Optical Cavity Modes from Uniformly Etched Porous Silicon
Authors: Doan Vincent V. , Curtis C. L. , Credo G. M. , Sailor M. J. , Penner R. M.
Published: March 2011

Uniform layers of porous silicon have been produced in a photoelectrochemical etch that show intensity enhancements of up to 100 fold, relative to samples etched in the dark. These films can also show fine structure in their photoluminescence (PL) spectra characteristic of longitudinal optical cavity modes. The highly luminescent, uniform porous layer is generated by illumination with blue or green light during the electrochemical etch of singlecrystal (B-doped) Si, and the enhancement is attributed to a localized photochemical etch process. The relevance of the increased PL intensity and interference-induced spectral changes to measurements of the intrinsic emission spectrum of porous Si are discussed.
Luminescence Studies of MBE Grown SI/SIGE Quantum Wells
Authors: Gail M. , Brunner J. , Menczigar U. , Zrenner A. , Abstreiter G.
Published: March 2011

We report on detailed luminescence studies of MBE grown Si/Si1-xGex quantum well structures. Both well width and composition is varied over a wide range. Bandgap photoluminescence is observed for all samples grown at elevated temperatures. The measured bandgap energies are in good agreement with subband calculations based on effective mass approximation and taking into account the segregation of Ge atoms during growth. Diffusion is found to limit quantum well (QW) growth with Ge-contents above 35% at high temperatures. The photoluminescence signals are detected up to about 100K and can be attributed to interband transitions of free excitons. We also present investigations of the exciton binding energy as a function of well width and composition. The observed shift of the exciton binding energy is compared with results of a variational calculation. A distinct onset in photocurrent and electroluminescence up to 200 K are observed in quantum well diodes.
Photoluminescence of Chemically Etched Polycrystalline and Amorphous Si Thin Films
Authors: Steckl A. J. , Xu J. , Mogul H. C.
Published: March 2011

Si thin films were deposited on quartz at temperatures ( TD ) ranging from 540 to 640°C. X-ray diffraction indicates that films deposited at TD < 580°C are amorphous, while those deposited above 600°C are poly-crystalline with a <220> texture. The Si films were made porous by stain-etching in HF:HNO3:H2O. Only Si films deposited at 590°C and above show photoluminescence (PL), centered at ∼650-670 nm under UV excitation. Films deposited at TD < 580°C do not luminesce even after very long etch times, which produce a highly porous structure. The PL intensity and the x-ray signal follow a very similar trend with TD. It appears that a minimum level of crystallinity is required for photoemission in porous Si and that a strong relationship exists between them.
Nonlinear Optical Properties and Fatigue Effect in Porous Silicon
Authors: Griviekas Vytautas , Kolenda Jonas , Misoguti Lino , Basmaji Pierre , Zilio Sirgio C.
Published: March 2011

We report results of photoluminescence (PL) fatigue and nonlinear optical absorption in anodized porous silicon (PS) samples aged in air for a few months. The fatigue strength is found different for PS emitting below 1.65 eV, in 1.65 - 2.05 eV range and above 2.05 eV, revealing the different nature of PL. A comparison with two special glasses is made, and a possible explanation for PL mechanism in PS is discussed.
Synthesis of Dislocation Free Siy(SnxC1−x)1−y Alloys by Molecular Beam Deposition and Solid Phase Epitaxy
Authors: He Gang , Savellano Mark D. , Atwater Harry A.
Published: March 2011

Synthesis of strain-compensated single-crystal Siy(SnxC1-x)1-y alloy films on silicon (100) substrates has been achieved with compositions of tin and carbon greatly exceeding their normal equilibrium solubility in silicon. Amorphous SiSnC alloys were deposited by molecular beam deposition from solid sources followed by thermal annealing. In situ monitoring of crystallization was done using time-resolved reflectivity. Good solid phase epitaxy was observed for Si0.98Sn0.01C0.01, at a rate about 20 times slower than that of pure silicon. Compositional and structural analysis was done using Rutherford backscattering, electron microprobe, ion channeling, x-ray diffraction, and transmission electron microscopy.
Simulation of A Low Loss Optical Modulator for Fabrication in Simox Material
Authors: Tang C K , Reed G T , Walton A J , Rickman A G
Published: March 2011

A novel phase modulator has been designed and analysed, assuming fabrication in a silicon-on-insulator material such as SIMOX. The proposed modulator is based upon a transverse p-i-n structure, utilising the plasma dispersion effect to produce the desired refractive index change in an optical rib waveguide. The device has been studied using the MEDICI two dimensional device simulation package to optimise the injected carrier interaction with the propagating optical mode. Whilst the device is designed to support a single optical mode, it measures several micrometers in cross sectional dimensions, thereby simplifying fabrication and allowing efficient coupling to other single mode devices such as optical fibers. Furthermore the device has an extremely high figure of merit, predicting over 200 degrees of induced phase shift per volt per mm. This implies a short active length together with a low power requirement.
Electroluminescence Evaluation of the SiO2-Si Structures Using an Electrolyte-SiO2-Si Cell
Authors: Baraban A.P. , Konorov P.P. , Bota S.A. , Morante J.R.
Published: March 2011

The use of an Electrolyte-SiO2-Si system allows a detailed control of the electron injection from the electrolyte into SiO2 layer, and makes feasible to reach the electron heating in the conduction band of SiO2 before to take place the irreversible breakdown.

The injected and heated electrons enhance the probability of the SiO2 defect excitation as well as the Si-O bond breaking. Both features give raise to the relaxation processes which are responsible of the electroluminescence characteristics of the oxide. So, the measured electroluminescence spectrum presents straightforward information on the defect types, their nature and possible precursor defect behaviour. Results on silicon oxides obtained from different technological processes and treatments, corroborate the above analysis and show the electro-luminescence of SiO2 as an interesting and powerful method to evaluate the SiO2 properties.
X-Ray Investigation of Strain Relaxation in Short-Period SimGen Superlattices using Reciprocal Space Mapping
Authors: Hamberger P. , Koppensteiner E. , Bauer G. , Kibbel H. , Presting H. , Kasper E. , Pesek A.
Published: March 2011

The optoelectronic properties of SimGen strained layer superlattices (SLS's) depend strongly on the structural perfection. We used double crystal and triple axis x-ray diffractometry to characterize the structural properties of short period Si9Ge6 SLS's grown on about lμm thick step-graded SiGe alloy buffers. As grown SLS's and samples annealed subsequently at 550°C, 650°C and 780°C for 60 mmn were investigated. Precise strain data were extracted from two-dimensional reciprocal space maps around (004) and (224) reciprocal lattice points. These data were used as refined input parameters for the dynamical simulation of the integrated intensity along the qll[004] direction. Annealing causes interdiffusion as indicated by the decreasing superlattice (SL)-satellite peak intensities and by the change of the Si/Ge thickness ratio. However, the full width at half maximum of the SL satellite peaks does not change significantly with annealing up to 650°C. The in-plane SL lattice constant in both samples is increased only slighty by annealing (< 9×10−3 Å). Consequently the interface intermixing due to interdiffusion is the main cause for the shift of the luminescence energy to higher values in these annealed samples.
Unimportance of Siloxene in Luminescent Porous Silicon as Determined by Nexafs & Exafs
Authors: Friedman S.L. , Marcus M.A. , Adler D.L. , Xie Y.-H. , Harris T.D. , Citrin P.H.
Published: March 2011

Near-edge-- and extended--x-ray absorption fine structure measurements, as well as luminescence excitation and emission spectra, were obtained from samples of porous Si and siloxene. Contrary to a recently proposed explanation for the room temperature luminescence in porous Si, the combined data indicate that siloxene is not principally responsible for the observed effect.
Comparative Study of Light-Emitting Porous Silicon Anodized with Light Assistance and in the Dark
Authors: Tsybeskov L. , Peng C. , Duttagupta S.P. , Ettedgui E. , Gao Y. , Fauchet P.M. , Carver G.E.
Published: March 2011

In this study, we compare two different types of light emitting porous silicon (LEpSi) samples: LEpSi anodized in the dark (DA) and LEpSi anodized with light assistance (LA). On the basis of photoluminescence (PL), Raman, FTIR, SEM, spatially resolved reflectance (SRR) and spatially resolved photoluminescence (SRPL) studies, we demonstrate that the luminescence in LA porous silicon is strong, easily tunable, very stable and originates from macropore areas. These attractive properties result from passivation by oxygen in the Si-O-Si bridging configuration that takes place during electrochemical anodization. In addition, we have been able to correlate light emission with the presence of crystalline silicon nanograins.
Enhanced Band-Gap Luminescence in Strain-Symmetrized (Si)m(Ge)n Superlattices
Authors: Menczigar U. , Abstreiter G. , Kibbel H. , Presting H. , Kasper E.
Published: March 2011

We report on band-gap luminescence in short period, strain symmetrized (Si)m(Ge)n superlattices grown on relaxed, step-graded Sil-xGex alloy buffer layers. The dislocation density in the superlattices, which were grown at 500°C using Sb as a surfactant, is reduced by 2-3 orders of magnitude compared with superlattices grown on thin, partly relaxed Sil-xGex buffer layers. Due to the improved quality of the superlattices, well defined band-gap luminescence could be observed which is for a (Si)6(Ge)4 superlattice strongly enhanced compared with a Si0.6Ge0.4 alloy reference sample. The measured band-gap energies compare well with theoretical predictions. To study the influence of interdiffusion of the Si- and Gelayers on the band-gap of the superlattices, the samples were annealed and studied with photoluminescence and Raman spectroscopy. An increasing band-gap and a decreasing luminescence efficiency was found with increasing intermixing of the layers. These experimental results are well described with an interdiffuision model of the layers in conjunction with an effective mass calculation.
Silicon Nanostructures in Si-Based Light-Emithing Devices
Authors: Namavar Fereydoon , Pinizzotto R.F. , Yang H. , Kalkhoran N. , Maruska P.
Published: March 2011

High resolution cross-sectional electron microscopy and electron diffraction of an np heterojunction porous Si device, capable of emitting light at visible wavelengths, clearly indicates the presence of Si nanostructures within the quantum size regime. These results indicate that the quantum confinement effect is at least partially responsible for photoluminescence at visible wavelengths.
Visible Photoluminescence From Porous Silicon Carbide
Authors: Matsumoto T. , Tamaki T. , Futagi T. , Mimura H. , Kanemitsu Y.
Published: March 2011

We have fabricated porous silicon carbide using single crystal 6H–SiC that has a wider indirect bandgap than silicon crystal prepared by electrochemical anodization. We have observed intense blue–green luminescence with the peak wavelength of around 500 nm at room temperature. The luminescence intensity is about five hundred times stronger than that of free electron to acceptor recombination in 6H–SiC crystal. This porous SiC offers an intense blue–green luminescent material. The results of structural analysis (secondary electron microscope analysis) and optical measurements (photoluminescence spectrum, Raman spectrum, and picosecond luminescence decay) suggest that the origin of the intense blue–green luminescence is the same as that of the intense red luminescence of porous silicon.
Characterization of Photoluminescence From Anodically Etched SiC/Si Heterostructures
Authors: Steckl A. J. , Su J. N. , Xu J. , Li J. P. , Yuan C. , Yih P. H. , Mogul H. C.
Published: March 2011

Patterned SiC/Si heterostructures have been treated by anodic etching in HF/ethanol solutions at 25°C. The anodic process used a current density ranging from 2-10 mA/cm2 and times from 2-5 min. The SiC/Si samples had SiC regions and exposed Si regions of dimensions from 2.5 μm to ∼500 gm. For μm substrates, short etching times (≥3 min) result in selectivcarea UV-induced visible photoluminescence (PL) being observed at 25°C from only the SiC regions. Longer etching times (≥3 min) render both the SiC-protected and the exposed Si regions photoluminescent, with nearly identical spectral characteristics and with a peak located at 660-670 nm. The selective-area PL is based on the rapid lateral etching of the n-Si surface under the SiC layer due to either high surface stress caused by the lattice mismatch between SiC and Si and/or to a higher SiC conductance. This is confirmed by the time progression of the PL images in the SiC regions. The PL degradation with UV exposure time has been shown to be substantially reduced by a passivation procedure involving HNO3/H2O. For SiC/p-Si structures, the exposed Si regions become photoluminescent upon very short anodization time, while the SiC regions did not luminesce at all for even the longest anodization times used (5 min).
Optical Studies of porous Silicon
Authors: Lin T. , Sixta M. E. , Cox J. N. , Delaney M. E.
Published: March 2011

The optical properties of both electrochemically anodized and chemically stain-etched porous silicon are presented. Fourier transform infrared (FTIR) spectroscopy showed that absorbance in stain-etched samples was 3x and 1.7x greater than in anodized samples for the SiH/SiH2 stretch and scissors-bending modes, respectively. Also, oxygen is detected in stain-etched samples immediately after formation, unlike anodized samples. Photoluminescence measurements showed different steady state characteristics. Electrochemical-etched silicon samples stored in air increased in photoluminescent intensity over time, unlike the stain-etched samples. A photoluminescent device made by anodization on epitaxial p-type material (0.4 Ωm) on n-type substrate (0.1 Ω-cm) did not exhibit electroluminescence.
Prospects for Infrared Electroluminescence From Porous Silicon
Authors: Koch F. , Kux A.
Published: March 2011

Efficient visible luminescence from porous Si requires the 3-dimensional confinement of charges in structures with typical ∼3nm size. Such microporously etched Si acts as an intrinsic wide-gap material and is highly resistive. The material does not have the good transport properties consistent with an efficient electrical excitation. We instead suggest to employ mesoporously etched, p+-type Si with its better conductivity in electroluminescence application. The material luminesces in two spectral bands centered about 0.8eV and 1.0eV in the infrared. Both emissions originate from surface-bound states. We report on the temperature dependence of luminescence, on transport and first attempts to generate infrared light by the injection of electrical current.
Oxygen-Enhanced 1.54μm Photoluminescence of Er+3 in Silicon
Authors: D'avltaya F. Arnaud , Campidelli Y. , Chroboczek J.A. , Favennec P.N. , L'haridon H. , Moutonnet D. , Wasiela A.
Published: March 2011

Favennec et al. (Jap. J. Appl. Phys. 29, L524, 1990) reported that the 1.54μm photoluminescence of Si implanted with Er+3 is activated by oxygen impurities. We observe a significant enhancement in the luminescence in Er-doped silicon epitaxial layers MBE-grown with intentional oxygen contamination. The PL is shown to be a bulk property of the material as it persisted after a partial layer removal by wet etching.
1.54 μm Photoluminescence of Erbium Implanted Hydrogenated Amorphous Silicon
Authors: Kechouane M. , Beldi N. , Mohammed-Brahim T. , L'Haridon H. , Salvi M. , Gauneau M.
Published: March 2011

The luminescence of erbium implanted in hydrogenated amorphous silicon (a-Si : H) is presented. For the first time an intense and relatively sharp luminescence at 1.54 mm is observed in a-Si : H, using implanted erbium. The Er+ emission intensity strongly depends on the hydrogen film content and on the measurement temperature. A direct correlation between the optical gap energy of the semiconductor and the hydrogen film content is observed.
Dependence of Residual Stress of Diamond-Like Carbon Films on Precursor Gases and Process Parameters of RF PACVD
Authors: Lee Kwang-Ryeol , Baik Young-Joon , Yong Eun Kwang
Published: March 2011

Residual compressive stress of diamond-like carbon (DLC) films was measured by beam deflection method. DLC films were deposited on thin Si wafers using r.f. plasma decomposition of methane and benzene. Negative bias voltage of the cathode was varied from -100 to -800 V and deposition pressure from 3 to 100 mTorr. When using benzene as precursor gas, the residual stress monotonically increases as increasing . (Here, Vb is the negative bias voltage of cathode and P the deposition pressure.) In case of using methane, however, the residual stress has a maximum value at between 70 and 100 V/mTorr1/2. Because of the difference in molecular size between benzene and methane, the mean free path of ions in benzene discharge is 5 times shorter than that in methane discharge. The contrasting behavior of residual stress is discussed in terms of the difference in ion energies at the specimen surface due to the difference in mean free path. On the other hand, total hydrogen concentration decreases as increasing in both cases. This result thus shows that the total hydrogen concentration cannot be a key to understand the behavior of residual stress.
Effects of Film Thickness and Annealing Temperature on the Stress in Amorphous Gd-Fe Alloy Thin Films
Authors: Zhou Zhi-feng , Fan Yu-dian
Published: March 2011

Gd-Fe films were deposited by magnetron sputtering on glass substrates. The results shoved that the stress is compressive in most cases, and a larger compressive stress exists at the film-substrate interface. The stress is independent on the film thickness when the film thickness is greater than 0.20 μm. The stress becomes tensile only when the annealing temperature attains 400ºC. Therefore, the interfacial stress and the growth stress coexist in the Gd-Fe films, and the former will not be dominant when the film thickness is greater than 0. 2μm. The interfacial stress may originate from the inhomogeneous distribution of film composition at the interface, and the origin of growth stress can be explained by the atomic peening effect. The relation between the stress and the annealing temperature can be comprehended with the amorphous structure model.
Mechanical Characterization of Thin Films Using Full-Field Measurement of Diaphragm Deflection
Authors: Pratt R. I. , Johnson G. C.
Published: March 2011

A new method for evaluating the elastic moduli and residual stresses in thin films is presented. This technique is based on measurement of the complete deflected shape of pressurized diaphragms made of the material to be evaluated. It offers important advantages over previous techniques in which only the displacement of the center of the diaphragm is measured as a function of pressure. The experimental apparatus uses a laser beam and its reflection from the sample surface to determine relative height. Measurements are made over an area of the sample by performing a two-dimensional scan of the sample under the laser beam. The most important advantage of determining the entire deformed shape of the diaphragm is that the shape is known rather than assumed. This way, the particular theory chosen to analyze the structural response does not also dictate a deformed shape based solely on the maximum deflection at the midpoint. Plate theory, as opposed to the more traditional membrane theory, is used to account for the dominance of bending behavior at low pressure and near the diaphragm edges. An energy method is employed to estimate stiffness and residual stress. The accuracy of this approximate method is directly related to how closely the assumed mode shape used in the analysis approximates the true response of the structure. Since these surface profiles are measured experimentally, the resulting property estimates are obtained with increased confidence.
Stress Measurements in Materials for Magnetic Recording
Authors: Raman V. , Coffey K.R. , Umphress R. , Howard J.K.
Published: March 2011

Investigations of the mechanical behavior of materials used in magnetic recording is of considerable practical importance in order to assure reliable file performance. With this objective, we have investigated the magnitude of the internal stresses observed in four sputtered thin film materials typically used in magnetic recording. First, the magnitude of the stresses observed in sputtered carbon films with and without hydrogen were measured and the nature of stress relaxation and thermal stability in different ambicnts were investigated. Second, the magnitude of the internal stress in CoPtCr magnetic media with and without a Cr-based sublayer that enhances magnetic performance was examined. Finally, the magnitude of stresses typically observed in thicker sputtered films of alumina were investigated both at room temperature and at elevated temperatures. The magnitude of the stresses observed in these sputtered films and their influence on mechanical performance are discussed.
Silicon Surface Micromachined Structures for the Stress Measurement of Thin Films
Authors: Mutikainen Risto , Orpana Markku
Published: March 2011

The realization of structures with silicon surface micromachining requires very low stresses of the structural elements. When low tensile film strains have been difficult to measure as no double-beam type structures susceptible for buckling at low tensile strains have been in use, a new “diamond beam” structure is proposed for the tensile-to-compressive strain conversion. The device performance is analysed as a strain gauge.

The micromachined structures can also be used as substrates for deposited films. The formulation is presented for double beam as substrate for deposited film compressive strain gauging. The structures were applied for strained sputter-deposited Molybdenum, and it was found that large undercut of the double beam edge must be avoided as well as the spacer film thickness must be large enough for beam buckling to be noticeable.
Accuracy and Reliability of Bulge Test Experiments
Authors: Small Martha K. , Vlassak Joost J. , Powell Stephen F. , Daniels Brian J. , Nix William D.
Published: March 2011

In this paper we address possible causes for inconsistencies in bulge test results and describe methods by which the bulge test technique can be made to produce accurate and reliable results. Experiments have been conducted on a variety of materials: polyimide (PIQ13) and polycarbonate (Lexan), silver and silver-palladium multilayers, and silicon nitride. All the materials tested yield biaxial moduli that are in the range of expected values for the bulk material. In addition, the tests show that the technique can be used to differentiate between the elastic properties of materials throughout the range of elastic stiffnesses, with even crystallo-graphic texture having a notable impact on the measured modulus. These results will be presented along with the methods used for preparing bulge test samples.
Modeling of the Blister Test to Express Adhesive Strength in Terms of Measurable Quantities
Authors: Sizemore Jim , Stevenson David A. , Stringer John
Published: March 2011

The adhesion of chemical vapor deposited (CVD) diamond thin films to substrates is a major limitation to using this new and exciting material. It is important to have a quantitative and absolute measurement of adhesive strength to understand and identify remedies. There are many methods to measure adhesion, but most rely on comparison to a standard instead of being an absolute measurement. The blister test is potentially able to measure adhesion both quantitatively and absolutely, but the existing analysis is not sufficient. This paper presents a fracture mechanics approach to analyze the blister test for a circular plate in order to obtain the appropriate quantitative information, i.e., the crack extension force,G. Several shape models exist. We consider several models to predict the behavior of this plate and then derive an equation that expressesGin terms of the critical pressure and critical volume at which de-bonding occurs. As a result of this analysis, we identify the key experimental parameters and show that this equation is insensitive to the model used.
A Simple Method for Determination of the Elastic Modulus of Thin Films on a Substrate
Authors: Swain M.V. , Weppelmann E.R.
Published: March 2011

High precision force displacement indenting instruments are now widely used for the determination of the mechanical properties of materials. However, for thin films attached to a substrate, the basis of any analysis of such high precision data is still limited. In this study the force displacement data has been generated using spherically tipped indenters of radii from 5 to 150 μm loaded onto a 2.74 μm thick TiN film on a silicon substrate as well as onto the substrate directly. Data have been generated using two loading procedures, continuous and load partial-unloading, almost entirely within the elastic contact regime. The results are analysed to determine the modulus of the TiN film.
Effect of the Substrate on Microindentation Behavior
Authors: Lardner T.J. , Ritter J.E. , Karamustafa H.B.
Published: March 2011

A continuous microindentation apparatus was constructed with a maximum load capacity of 45 N (resolution of 0.1 N) and with a maximum displacement of 500 μm (resolution of 2.0 μm) and used to test bulk materials (brass, aluminum, steel, soda-lime glass and PMMA) and epoxy coatings on substrates of aluminum, steel, soda-lime glass and PMMA. The hardness (H) was determined with a Vickers indenter and compared to that obtained with a Tukon hardness tester. The elastic modulus of the coated systems was also estimated from the unloading curves. In general, we found that the indentation behavior of the epoxy coated system was influenced by the substrate with softer substrates (as with PMMA) being deformed before the indenter penetrates the coating. With all coated systems, the on-load value of H was independent of the penetration depth until the indenter penetrated the substrate. For the aluminum, steel and soda-lime glass substrates, the value of H after penetration increased slowly due to the pile up of the epoxy coating underneath the indenter supporting more of the load. For the PMMA substrate, hardness decreased after penetration because the hardness of PMMA was less than the epoxy coating.
Real Time Stress Measurements During Growth of Aluminum Nitride on SI(111) and SI(001)
Authors: Meng W. J. , Sell J. A. , Eesley G. L. , Perry T. A.
Published: March 2011

We have performed real time measurements of intrinsic stresses during growth by reactive dc magnetron sputtering of aluminum nitride (AlN) thin films on silicon substrates in an UHV growth chamber. An experimental setup based on laser beam reflection is constructed such that substrate curvature as well as film thickness can be continuously monitored as growth proceeds. On Si(111) substrates, stress measurements were carried out during growth of both polycrystalline and epitaxial A1N films as a function of deposition pressure. This is the first such comparative study to our knowledge for the AlN/Si system. Our room temperature measurements on polycrystalline films corroborates previous post-growth measurements. Our high temperature measurements provide evidence of large intrinsic stresses and negligible stress relaxation during epitaxial growth of AlN on Si(111). We further compared stress behavior during both room temperature and high temperature growth of AlN films on Si(111) and Si(001) substrates. Our observations indicate while intrinsic stresses during room temperature growth can be compressive or tensile depending on plasma conditions, it is tensile during late stage growth at high temperatures.
Micro-Wear Technique and its Application to Ultra Thin Film Systems
Authors: Wu T.W. , Lee C.-K.
Published: March 2011

A micro-wear testing technique has been developed by incorporating a piezoelectric pusher into an existing micro-indenter system. The pusher and its associated servo-control circuitry were designed to generate a precise reciprocating horizontal motion at the indenter tip for implementing micro-scaled wear test. The information acquired from the test includes the wear loading curve, i.e., the normal applied load versus wear penetration depth, the friction force and in turn, the apparent wear friction coefficient. Acquiring the electrical resistance across the coating thickness is also possible if an electrical conducting indenter is utilized. Furthermore, in collaboration with the surface characterization tools, the wear morphology revealed useful information regarding the coating failure mechanism(s) and shed some light towards understanding coating tribology. The tester design concepts, operating procedure, data acquisition and analysis will be examined. Experimental results on ultra thin carbon coatings with various thicknesses will be employed to illustrate the capabilities of the microwear tester.
Validity of Adhesion between Films and Substrate with Friction-Detected Scratch Test
Authors: Wang Ru
Published: March 2011

The validity of Lc of film failure is studied with friction — detected scratch test . The specimens used in the experiment are ion-plated TiN and Ti films,Chemical-Plated NiPCu films on steel of various hardness,ion beam mixed plated TiN films on optical glass,The morphology of failed films was studied under optical microscope and scanning electronmicroscope,The composition of starting failure of films was analyzed with electro — probe. It is found that in the curves of scratch tests of ion-plated TiN and Ti films on high-speed steel,the load corresponding the sudden change of the horizontal force is the same as the critical load of film failure,however,the critical load obtained in the scratch test of the ion-plated TiN and Ti films on soft steel is the some deference compared with optical microscope analyzed, that is principally due to the property of films and substrates (hardness and coefficient).

The morphology and mechanism of ion — plated TiN and Ti films on high —speed steel are also studied in the paper.

The adhesion between film and substrate is an effective method in evaluating the films property. After apprasing the effectiveness of acoustic emission monitoring scratch test, someone think that no matter coated with hard or soft film it is effective on the brittle hard substrate. However,there exist errors to different extent on other film-substrate system,and the scratch test is inapplicable for soft film-soft substrate system[1]. P. A. Steinmann pointed out while studying the factors influnceing the critical load Lc,that friction coefficient is a key factor on Lc,it provided valuable information in measuring Lc,but it think it is imporsible to measure Lc totally dependent on sudden change friction or friction coefficient, howeveer, for a specific coating substrate system,it is acceptable to say that Lc is dependent on friction coefficient[2]. This paper study experimentally on the friction detected scratch test and found out that effectiveness of Lc varies substantially in different film-substrate system. The author studiied the regularity of various system and discuse the season. The failure morphology and principles of ion-plated TiN and Ti film on highspeed steel are also analyzed in this paper.
Strain Relaxation and In-Situ Observation of Voiding in Passivated Aluminum Alloy Lines.
Authors: Besser Paul R. , Marieb Thomas N. , Bravman John C.
Published: March 2011

Strain relaxation in passivated Al-0.5% Cu lines was measured using X-ray diffraction coupled with in-situ observation of the formation and growth of stress induced voids. Samples of 1 μm thick Al-0.5% Cu lines passivated with Si3N4 were heated to 380ºC, then cooled and held at 150ºC. During the test, principal strains along the length, width, and height of the line were determined using a grazing incidence x-ray geometry. From these measurements the hydrostatic strain in the metal was calculated and strain relaxation was observed. The thermal cycle was duplicated in a high voltage scanning transmission electron microscope equipped with a backscattered electron detector. The 1.25 μm wide lines were seen to have initial stress voids. Upon heating these voids reduced in size until no longer observable. Once the samples were cooled to 150ºC, voids reappeared and grew. The measured strain relaxation is discussed in terms of void and θ-phase (Al2Cu) formation.
Analysis of Stresses at Singular Points of Patterned Structures.
Authors: Chouaf A. , Loppin G. , Ignat M. , Terriez J.M.
Published: March 2011

An iterative method describing the stress state at the vicinity of singularity point is presented here. This approach is based on concepts of rupture mechanics, uses classical solutions from finite element calculations and concerns plane problems. Through this approach, the stress state at the vicinity of several types of singular points in a patterned structure were analysed. The obtained results can be discussed according to failure mecanisms.
Analysis of Thermal Stress Induced Void Growth During Thermal Cycling
Authors: Brown D.D. , Korhonen M.A. , Børgesen P. , Li C.-Y.
Published: March 2011

Recent work in thermal stress induced voiding in passivated lines has focussed on the isothermal, quasi-steady state growth of existing voids. In this work, the transient growth and shrinkage of voids during the thermal cycling of narrow, passivated lines was studied. Analysis of experimental data for passivated lines demonstrates the quick buildup and evolution of a backstress at the grain boundary during heating and cooling. This backstress greatly reduces the driving force for void growth at higher temperatures and must be accounted for in stress induced void growth models for the case of appreciably varying temperatures in short time scales.
Determination of the Mechanical Response of Thin Films with X-Rays
Authors: Noyan I. C. , Sheikh G.
Published: March 2011

The mechanical response of a specimen incorporating thin films is dictated by a combination of fundamental mechanical parameters such as Young's moduli of the individual layers, and by configurational parameters such as adhesion strength at the interface(s), residual stress distribution and other process dependent factors. In most systems, the overall response will be dominated by the properties of the (much thicker) substrate. Failure within the individual layers, on the other hand, is dependent on the local strain distributions and can not be predicted from the substrate values alone. To better understand the mechanical response of these systems, the strain within the individual layers of the thin film system must be measured and correlated with applied stresses. Phase selectivity of X-ray stress/strain analysis techniques is well suited for this purpose. In this paper, we will review the use of the traditional x-ray stress/strain analysis methods for the determination of the mechanical properties of thin film systems.
Grain Boundary Sliding in Thin Substrate-Bonded AL Films
Authors: Prieler M. , Bohn H.G. , Schilling W. , Trinkaus H.
Published: March 2011

A systematic investigation of the anelastic relaxation of thin Al films on Si substrates has been carried out. It was found that both the relaxation in bulk and thin film material can be explained by a model involving glide of grain boundaries (GBs). The mass transport necessary for the glide occurs via GB diffusion in the thin films and via lattice diffusion in the bulk material the different behavior being due to the more of two orders of magnitude smaller grains in the films. Internal friction thus provides a technique to measure diffusional parameters of GB diffusion in thin films.
Effects of Confinement on Plastic Deformation in Passivated AL Films
Authors: Anderson S.G.H. , Yeo I.-S. , Ho P.S. , Ramaswami S. , Cheung R.
Published: March 2011

Wafer curvature measurements of a trilayer (SiO2 / AlSiCu / Si) structure are compared to that predicted by a weighted sum of individual measurements of SiO2 and AlSiCu films on Si, and significant differences are found to exist for temperatures above 200°C. A straightforward analysis of the stresses in each layer has been modeled using an extension of a model by Feng et al. which assumes uniform plastic deformation throughout the Al. The modeling results suggest a straightforeward method for determining stresses in deformable thin films that are confined by elastic overlayers. A comparison of the stress-temperature behavior for unpassivated and passivated AlSiCu films reveals that the confined films exhibit less plastic deformation and both higher tension and compression during thermal cycling.