bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study on the Strain and Microstructure in SiGe Film Grown on Si(001) Substrate by MBE
Authors: Cho Kyoung-Ik , Nahm Sahn , Kim Sang-Gi , Lee Seung-Chang , Kim Kyung-Soo , Park Sin-Chong 
Published: April 2011

AbstractSi/Si0.8Ge0.2/Si(001) structures were grown at various growth temperatures (250 ∼ 760 °C) using molecular beam epitaxy, and the variation of strain and microstructure of the film was investigated using double crystal X-ray diffractometry and transmission electron microscopy. SiGe films with good single crystallinity were obtained at the growth temperatures of 440 ∼ 600 °C. For the samples grown below 350 °C, an amorphous SiGe film was developed over the SiGe single crystalline layer with a jagged amorphous/crystalline (a/c) interface, and many defects such as stacking faults and microtwins were formed below the a/c interface. Dislocations were developed through out the films for the samples grown above 680 °C. In addition, for the samples grown below 680 °C, the amount of in-plane strain of the SiGe film was found to be about − 8×l0−3 without strain relaxation. However, the SiGe films grown at 760 °C have small in-plain strain of − 4×l0−3 and large strain relaxation of 50%.
Calculation of the (GaAs)m(AlAs)n Superlattice Piezoelectric Constants
Authors: Mirovitskii Vadim. Yu. 
Published: April 2011

AbstractA new method for calculation of superlattice (SL) piezoelectric properties is proposed. It is used for derivation of the piezoelectric constants of ultrathin [001] oriented (GaAs)m(AlAs)n SL. These SL are formally considered to result from complete ordering Ga (Al) atoms over a-positions of a hypothetical initial structure of a bulk mixed crystal of (GaxAl1-x)As with x=m/(m+n). This viewpoint allows us to develop a method which is close to the Landau phenomenological theory of second- order phase transitions and which is intended for calculation of the SL crystal-lophysical constants. It is shown that a nontrivial term has much significance in changing one of the piezoelectric constants, γz,xy, when the initial structure is transformed into a SL. This term is composed of coefficients at three translational invariants (Dzyaloshinskii invariants) in the expansion of the thermodynamic potential of the “ordering” system in a power series of the order parameter components. The values of these coefficients must be obtained from microscopic calculations which take account of spatial correlations in Ga(Al) atomic distribution. Specific calculations are carried out for a SL with m+n=3.
Effect of Annealing on High Frequency Viscoelastic Waves in Spincoated Polymer thin Films
Authors: Dutcher J. R. , Wang Z. , Neal B. J. , Copeland T. , Stevens J. R. 
Published: April 2011

AbstractWe present a study of the effect of elevated temperatures on the high frequency viscoelastic waves guided by thin films of poly(styrene) [PS] and poly(methyl methacrylate) [PMMA]. The films, which are spincoated onto Si(OOl) wafers, have thicknesses h ˜ 1000 Å. The frequencies and linewidths of the film-guided waves were measured using Brillouin light scattering (BLS). In both PS and PMMA, we observed guided waves for temperatures above the glass transition temperature Tg of the polymers, however, the damping of the waves for temperatures above Tg was significantly higher for PS. We observed no significant (< 1 %) difference between room temperature guided-wave frequencies for films annealed at temperatures below and above Tg for PS, and a slight (4 %) increase in the wave frequency for PMMA following annealing at a temperature above Tg. The heating effects due to the focussing of the laser beam on the film surface are quite small (˜ 16°C/100 mW laser power).
Temperature Dependence of Residual Stresses and Stress Relaxation in Blanket Films of Various Thicknesses
Authors: Clarke A. P. , Langelaan G. , Saimoto S. 
Published: April 2011

AbstractA rapid method to measure residual strains using x-rays during continuous temperature ramping has been developed whereby resolution of ±5xl0-5 can be attained with 2θ scans of about one minute using low index reflections. The method was used to make residual stress measurements during temperature cycling at heating rates of 2 to 15°C/min with interrupted stress relaxations at 235°C and 130°C on pure Al blanket films of 0.24μm, 0.58μm and 1.01 μm thicknesses. The results are consistent with the notion that surface sources are activated by the back stress of misfit dislocations.
Maskless Single-Sided Wet Etching Process for the Fabrication of Ultra-Low Distortion Polyimide Membranes
Authors: Schattenburg M. L. , Fuentes R. I. , Czernienko G. , Fleming R. C. , Porter J. 
Published: April 2011

AbstractA process for volume production of ultra-low distortion (<200 ppm), thin polyimide membranes on silicon wafers was developed using the RotoEtch™ dynamic fluid confinement tool. A critical advantage of the process is that it exposes the sample to the etching solution over a selected area on one side only, without contacting, wetting, or otherwise contaminating the front surface. This unique feature allows the etching away of a circular portion (over 40 mm diameter) of the backside of a patterned silicon wafer to form a freestanding thin polyimide membrane (<1 μim thick). The polyimide film is patterned prior to wet etching with a sub-micron period grating (200 nm period). The resulting distortion of the grating on the freestanding membrane is less than 200 ppm over the entire membrane area. This process seems ideally suited for instances—like the one above—when immersion, contacting, or contamination of one side of the sample would be impossible or impractical. It also allows backetching finished micro-structures that would otherwise be disturbed or destroyed by immersion in the fluid. Finally, it speeds up the fabrication of freestanding films since it does not require masking or any other form of front-side protection or backside lithographic steps. In this paper we report on a silicon through-etch process based on an HF:HNO3 acid mixture which typically forms membranes in only 10–20 minutes. Since polyimide easily distorts due to excessive heat or mechanical strain, the etching process needs to be carefully controlled. This process is also ideal for forming large membranes of other HF:HNO3-inert materials such as silicon carbide or diamond.
Instability Analysis of Strained Interfaces Via a Discrete Atom Method
Authors: Lee Jong K. 
Published: April 2011

AbstractThe morphological instability of an epitaxially-strained, thin film is studied by means of a discrete atom method in a dislocation-free, two-dimensional crystal. The instability of the film-substrate interface is also examined in conjunction with the migration of the free surface. The results show that a mobile film-substrate interface can accelerate merger between the two surfaces, and anisotropic effects facilitate island formation. In addition, the instability of a curved interface is discussed with the results on the morphological evolution of coherent precipitates. A circular, soft precipitate in an isotropic matrix undergoes a series of shape transitions before reaching its equilibrium shape. As in the strained thin film case, transition begins with interfacial waves induced by the coherency strain. The waves then develop small lobes, which coarsen into a lower density of larger lobes. The larger lobes eventually coarsen as the equilibrium shape is approached. Anisotropic effects suppress some of the interfacial waves.
Indentation at the Nanometer Scale on Ultra Thin Films of Diamond-Like Carbon
Authors: Bec Sandrine , Tonck André , Loubet Jean-Luc 
Published: April 2011

AbstractUltra thin films (50 nm and 180 nm) of amorphous diamond-like carbon on a silicon substrate produced by laser ablation are tested by nanoindentation with a new instrument deriving from a Surface Force Apparatus. Quasi-static measurements of the load and dynamic measurements of the contact stiffness are continuously and simultaneously recorded versus the penetration depth. Scanning lines on the tested surface before and after indentation are made by means of tangential displacement of the diamond indenter on the surface.The tests are conducted with maximum loads from 50 μN to 2500 μN, which correspond to maximum indentation depths between 7 nm and 70 nm. The indentation curves show near elastic recovery but scanning lines and/or topographic images on the surfaces show detectable plastic prints. Despite the extremely small residual indentation depths for these ultra thin films, we show how the hardness value we calculate from the indentation curves with an elastoplastic theory is in good agreement with the hardness value we calculate from the indentation print profile. The determination of the Young's modulus, even at the smallest indentation depths, must take into account the mechanical properties of the substrate. The determination of both values, hardness and elastic modulus, also requires a calibration procedure for the geometry of the tip and knowledge of the piling-up effect.We find that the apparent hardness and the apparent Young's modulus of the tested diamondlike films are high. They are underestimated in comparison with the real values. A rough correction which overestimates the Young’s modulus gives higher values than those of natural diamond.
Indentation behavior of a Brittle Film/Brittle Substrate Composite
Authors: Czarnik C. M. , Gibala R. , Baron O. , Nastasi M. , Jervis T. R. 
Published: April 2011

AbstractSurface-film induced plasticity caused by the generation of dislocations at the film-substrate interface has been demonstrated previously for bcc metals and B2 ordered alloys deformed at low homologous temperatures. More recently, we have observed similar effects at elevated temperatures for ZrO2-coated MoSi2, which also demonstrates a film-induced reduction in hardness for microhardness tests over 25°C - 1300°C. In this investigation, 120 nm - 480 nm thick ZrO2 films were deposited on (001) single crystal MoSi2 by electron beam deposition. These composites were used to characterize the film-induced softening of MoSi2 at room temperature, where both MoSi2 and ZrO2 are brittle. Indents were made through the film into the substrate at 0.5 kgf loads using Vickers and Knoop indenters. Atomic Force Microscopy was employed to measure the geometry of Knoop indents after load removal, and to compare the results to the loaded indentation shapes. Increasing film thickness reduces the length of radial cracks in the substrate and lowers the composite hardness. The film also changes the relative amounts of deformation associated with material pileup at the surface near the edges of the indent, suggesting a change in deformation mechanism from pileup around the indenter edges to deformation by dislocation motion in the bulk.
Nanoindentation and Nanoscratching of Hard Coating Materials for Magnetic Disks
Authors: Tsui T. Y. , Pharr G. M. , Oliver W. C. , Chung Y. W. , Cutiongco E. C. , Bhatia C. S. , White R. L. , Rhoades R. L. , Gorbatkin S. M. 
Published: April 2011

AbstractNanoindentation and nanoscratching experiments have been performed to assess the mechanical and tribological behavior of three thin film materials with potential application as wear resistant coatings for magnetic disk storage: (1) hydrogenated-carbon (CHx); (2) nitrogenated-carbon (CNx); and (3) boron suboxide (BOx). The hardness and elastic modulus were measured using nanoindentation. Ultra-low load nanoscratching tests were performed to assess the relative scratch resistance of the films and measure their friction coefficients. The mechanical and tribological performance of the three materials are discussed and compared.
Dislocation Emission at Surfaces
Authors: Beltz G. E. , Freund L. B. 
Published: April 2011

AbstractAn exact expression for the elastic energy associated with a semicircular shear dislocation loop emanating from a free surface, such as that of a stressed thin film, is derived (within continuum dislocation theory) and compared with earlier approximations. The energy required to activate a semicircular dislocation loop into its unstable “saddle-point” configuration is then re-calculated, based on the modified expression for the self-energy. It is found that the shear stress necessary to emit a loop, as a function of temperature, is almost 50% less than earlier estimates. The effects of ledges on the surface, as well as loop geometry, are discussed. The principal drawback to this type of calculation is pointed out, namely, that the critical radius of an incipient dislocation loop can be on the order of one atomic spacing, which is too small for a continuum theory to be valid.
Fabrication of Thick, Sol Gel Pzt Films: Applications to Macroscopic Piezoelectric Devices
Authors: Barrow D.A. , Petroff T.E. , Sayer M. 
Published: April 2011

AbstractLead zirconate titanate (PZT) films of up to 60 μm in thickness have been fabricated on a wide variety of substrates using a new sol gel process. The dielectric properties (∈ = 900), ferroelectric (Ec = 16 kV/cm and Pr = 35 μC/cm 2) and piezoelectric properties are comparable to bulk values. The characteristic Curie point of these films is at 420 °C. Piezoelectric actuators have been developed by depositing thick PZT films on both planar and coaxial substrates. Stainless steel cantilevers and optical fibres coated with a PZT film exhibit flexure mode resonant vibrations observable with the naked eye. A low frequency in-line fibre optic modulator has been developed using a PZT coated optical fibre. The high frequency resonance of a 60 μm film on a aluminum substrate has been observed.
Magnetomechanical Properties of Circumferentially Field-Annealed Metglas® 2605SC Cylinders
Authors: Restorff J. B. , Wun-Fogle M. , Clark A. E. , Luu Thu-Van T. 
Published: April 2011

AbstractWe have measured the magnetomechanical coupling coefficient of Metglas®2605SC (Fe81B13.5C2) ribbons that were annealed into 1.27 and 0.8 cm diameter cylinders. Lengths ranged from 0.6 to 5 cm. A novel furnace was constructed in which a cylindrical magnetic field was supplied by a current carrying copper rod. During the annealing, a 300 A current created a circumferential field of more than 6400 A/m. Annealing temperatures ranged from 380 to 420 ºC. Large shifts in both the optimum bias field and the coupling coefficient as a function of length and diameter were found due to demagnetizing effects. Impedance vs. frequency measurements show large numbers of modes, some of which are field dependent. Effective coupling coefficientsof the lowest order longitudinal mode were calculated from impedance measurements by using k2 = 1-f2r/f2a, where fr, and fa. are the resonant and antiresonant frequencies respectively. Coupling coefficients for 5 cm long cylinders were as high as 0.58. When the demagnetizing factor is taken into account, we find material coupling coefficients as high as 0.89.
Magnetostrictive Methods of Detecting Torque from Case-Hardened Steel Shafts
Authors: Sasada Ichiro 
Published: April 2011

AbstractThis paper begins with a review of the current problems associated with the application of conventional magnetic-head-type shaft torque sensors. These sensors were first proposedin 1954. Newly developed low-profile magnetic heads for torque sensors which address the problems of the older type of sensors are then presented. The torque sensor which uses the lowprofile pick-up heads is described in detail. Experimental results showing the basicperformance of the torque sensor with carburized nickel chromium molybdenum steel shafts (SNCM 420 in JIS) are then described. In this combination of the heads and the shaft, thehysteresis of the inputoutput relationship is generally small and shows that the direction of traversal around the hysteresis loop changes as the amplitude of the excitation current changes. It is shown that an optimum operating condition exists for the torque sensorin which the hysteresis achieves a minimum value yet the sensitivity remains high. In a particular combination studied in this paper, the optimum excitation current was 0.3 A at the excitation frequency 60 kHz, where the total power loss at the pick-up heads was 0.37W. Under this operating condition, the hysteresis was extremely small, and the linearity was better than 0.6%.
High Precision Actuator with Tb0.27Dy0.73Fe1.95 Single Crystal
Authors: Li Qiang , Chang Y.L. , Ouyang Shixi , Huang X.H. 
Published: April 2011

AbstractIt has been proved that the saturation magnetostrictive constant λs of Tb0.2 7Dy0.73Fe1.95 single crystal is greater than the polycrystal and grains oriented crystal with the terfenol compositions, especially for its large linear magnetostrictive strain. Th0.27Dy0.73Fel.95 single crystal also can produce large force and fast, precision motion at high efficiency and power levels. A proto-type micro positioning actuator with the single crystal was designed inour lab. The structure and performances are discussed in this paper.
Ultrasonic Appucations Using Magnetostrictive Smart Materials
Authors: Hansen T. Toby , Ghorayeb Solomon R. 
Published: April 2011

AbstractMany of the innovations in ultrasonic technology make use of modem smart alloys and materials. As a result, the theory and application of ultrasonic energy have become extremely important in various disciplines such as ultrasonic surgery, deaning and imaging. However, despite the fact that most of these ultrasonic devices are based on widely known materials, there remains a class of materials which have not been fully explored as potential active components in ultrasonic designs. In this paper, the giant magnetostrictive smart material, ETREMA TERFENOL-D®, is discussed to illustrate its potential for such applications. Frequency analysis, reliability and advantages of ultrasonic mechanisms using ETREMA TERFENOL-D® are also shown for a general broadband ultrasonic device. Frequencies between 1 kHz and 30 kHz were obtained for these applications.
Dynamic Shear Characterization in a Magnetostrictive Rare Earth - Iron Alloy
Authors: Bouchilloux Philippe , Lhermet Nicolas , Claeyssen Frank 
Published: April 2011

AbstractA previous study about the power limits of the magnetostrictive alloy called Terfenol-D, using a device biased by coils, showed the intrinsic superiority of this material compared to piezoelectric ceramics when used in high power sonar transducers. This fact was confirmed by another study where giant dynamic peak-to-peak deformations of 3500 ppm were measured with a transducer biased by permanent magnets.Experience shows that the longitudinal functioning of magnetostrictive transducers is sometimes disrupted by interference caused by ‘flexure’ in the magnetostrictive rods. In fact, due to the shape of the rods, the flexure effects are strongly coupled to shear. Characterization of shear in Terfenol-D under conditions of magnetic bias and prestress is then necessary to control those effects. This was made possible by using a simple and original device that was designed totally with Computer Aided Design programs.
A Facility For Evaluation of Actuators Based on Giant Magnetostrictive Materials
Authors: Tiberg H. , Engdahl G. 
Published: April 2011

AbstractThe recent development of actuators based on giant magnetostrictive materials in for instance hydroacoustic transducers has caused an increase in output forces from the drive elements used. The high stress levels make testing of the actuators with well defined mechanical loads difficult. The need for standards and improved evaluation methods has therefore become evident.Based on experiences from earlier test facilities a new set-up has been designed with the intention to obtain- higher resonance frequency- facilitated assembly of test objects- increased operating forces- flexible choice of mechanical loads- computer controlled measurement procedure- controllable environmental conditions, for instance temperature.In order to achieve the specifications, the test rig involves hydraulics for prestressing and clamping of the test object and the mechanical load. A method of mechanically disconnecting the prestress device from the fixture gives lower mass to stiffness ratio in the fixture and therefore a better high frequency performance.The presented test rig is considered to have the prerequisites of serving as a platform for future evaluation and standardization of actuators.
Carbon Fiber Reinforced Concrete as an Intrinsically Smart Concrete for Damage Assessment During Dynamic Loading
Authors: Chen Pu-Woei , Chung D.D.L. 
Published: April 2011

AbstractConcrete containing short carbon fibers (0.2-0.5 vol.%) was found to be an intrinsically smart concrete that can sense elastic and inelastic deformation, and fracture. The signal provided is the change in electrical resistance, which is reversible for elastic deformation and irreversible for inelastic deformation and fracture. The presence of electrically conducting short fibers is necessary for the concrete to sense elastic or inelastic deformation, but the sensing of fracture does not require fibers. The fibers serve to bridge the cracks and provide a conduction path. The resistance increase is due to conducting fiber pull-out in the elastic regime, conducting fiber breakage in the inelastic regime, and crack propagation at fracture.
Magnetic and Magnetoelastic Properties of Highly Magnetostrictive Amorphous Films with TbFe-FeB-TbFe Sandwich Structure
Authors: Igari T. , Ishii S. , Inoue M. , Fujii T. 
Published: April 2011

AbstractAmorphous Tb40Fe60-Fe80B20-Tb40Fe60 sandwich films were prepared by multitarget rf magnetron co-sputtering. Their magnetization and magnetostriction were studied to examine whether magnetic softening of the amorphous TbFe films could be achieved without loosing their giant magnetostriction by introducing the simple sandwich structure. The results revealed that a considerably soft in-plane magnetization (coercive force H≈ 6Oe and the squareness ratio Mr/Ms≈ 0.8) and a huge magnetostriction (λ >500ppm) could be obtained in the sandwich films at room temperature, provided that the thickness of the FeB interlayer was within the range of 10% to 40% of the total film thickness (1 μm).
Engineering Considerations in the Application of NiTiHf and NiAI as Practical High-Temperature Shape Memory Alloys
Authors: Russell Scott M. , Sczerzenie Frank 
Published: April 2011

AbstractNiTiHf and NiAI have shown the potential for development as high temperature shape memory alloys with transformation temperatures of 150°C or higher. However, various engineering considerations must be addressed before these systems can be used as practical high temperature shape memory alloys. These considerations include: fabricability, phase stability, mechanical stability, and cost. NiTiHf is attractive from a cost standpoint, although its fabricability must still be demonstrated on larger heats of material. The phase stability and mechanical stability of NiTiHf are unknown. NiAl requires great improvements in both fabricability and phase stability. The mechanical stability and costs for producing NiAI shape memory alloys are still unclear.
Smart Damping Treatment for Flexible Structure
Authors: Chen Q. , Levy C. 
Published: April 2011

AbstractThe mathematical model of a flexible cantilever beam with a constrained viscoelastic layer and shape memory alloy layer called smart damping treatment (SDT) is presented. It is shown that a change of the elastic modulus of the shape memory alloy layer will affect the system loss factor and resonance frequency. The recovery stress of the SMA layer leads to an inhomogeneity in the governing differential equation. The recovery stress also functions as an excitation to the system. The effects of the different parameters found in the analysis are discussed in the paper.