bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Properties of Excimer Laser Modified Titanium Surfaces
Authors: Jervis T. R. , Zocco T. G. , Hubbard K. M. , Nastasi M. 
Published: March 2011

ABSTRACTExcimer laser processing enables both thermally-driven transformations and the incorporation of solutes into the surface of materials through melting and diffusional mixing. We have examined the effect of excimer laser processing on the microstructure and surface mechanical properties of titanium alloys. Changes in the surface hardness due to laser processing were studied using a Nanoindenter™. Alloying experiments using both mixing of evaporated surface layers of boron and laser gas alloying in air and in nitrogen all result in changes in the surface hardness of the material. Alloying with boron results in an amorphous surface which is somewhat harder than the as polished surface. Laser processing in air and pure nitrogen results in incorporation of oxygen and nitrogen and the development of fine precipitates of TiO and TiN respectively. Substantial increases in surface hardness result due to solution and precipitation mechanisms. Nanoindenter™ data from several depths in the material are correlated with microstructure and solute concentration to illuminate the strengthening mechanisms involved.
Hrem Study of Fracture and Deformation Behavior of Nanostructured Thin Films
Authors: Ke Ming , Milligan Walter W. , Hackney Stephen A. , Carsley John E. , Aifantis Elias C. 
Published: March 2011

ABSTRACTNanocrystalline gold and nickel thin films were prepared by both ion beam sputter deposition and electron beam evaporation techniques. The grain sizes were between 8–60 nm, depending on the processing. The deformation and fracture behavior of these nanostructural thin films were then investigated in a high resolution electron microscope (HREM) with atomic resolution. The behavior was a strong function of grain size. During slow strain rate deformation of small grain size materials (< 25 nm), nanopores formed and grew at grain boundary triple junctions in the front of crack and eventually linked with the main crack. The coalescence of the main crack with the growing nanopore, along with the elimination of the ligament between the two by a diffusive process, both indicated that diffusion played a role in deformation and fracture of these nanocrystalline thin films. In nickel films with larger grain sizes (> 25 nm), the cracks propagated in a mixed mode which was partially intergranular and partially transgranular. The transgranular propagation was crystallographic in nature, showing very fine, distinct crystallographic facets on the crack faces. It is suggested that a transition from intergranular propagation to a “cleavage-like” mechanism of propagation occurs with the increase of grain size.
The Role of Indentation Depth on the Measured Hardness of Materials
Authors: Shell De Guzman Melissa , Neubauer Gabi , Flinn Paul , Nix William D. 
Published: March 2011

ABSTRACTUltra micro-indentation tests on Ni and Cu samples showed increasing hardness with decreasing penetration depth over a range from 200 to 2000 nm. The results suggest increased strain hardening with decreased indentation depth. To establish that this is a real material effect, a series of tests were conducted on amorphous materials, for which strain hardening is not expected. The hardness of Metglas® was found to be independent of depth. A simple model of the dislocation densities produced under the indenter tip describes the data well. The model is based on the fact that the high density of dislocations expected under a shallow indentation would cause an increase in measured hardness. At large depths, the density of geometrically necessary dislocations is sufficiently small to have little effect on hardness, and the measured hardness approaches the intrinsic hardness of the material.
Adhesion Properties of Metallic and Oxide Thin Films Produced by Several Methods
Authors: Ottermann C. , Tadokoro N. , Tomita Y. , Bange K. 
Published: March 2011

ABSTRACTAdhesion of Cr, SiO2, TiO2 and Ta2O5 films with thicknesses between 40 nm and 380 nm has been investigated using a new scratch-test method based on a vibrating diamond micro-indenter. The oxide films are produced on different substrates by sol-gel technique (SG), reactive evaporation (RE), reactive ion plating (IP) and plasma impulse chemical vapor deposition (PICVD); Cr-layers are deposited by sputtering (SP) on quartz. Large variations in adhesion are found for different coating techniques and deposition conditions, especially the substrate temperature. The adhesion can be correlated with microscopic properties in the film-substrate interface where differences are analyzed in term of hydrogen content, film growth and density. The adhesion is also connected with other macroscopic film quantities.
Stress-Corrosion Cracking and Blistering of Thin Polycrystalline Silicon Films in Hydrofluoric Acid
Authors: Monk D.J. , Krulevitch P. , Howe R.T. , Johnson G.C. 
Published: March 2011

ABSTRACTThin (0.1 μm) LPCVD polycrystalline silicon (poly-Si) films are shown to exhibit permeability and suffer structural degradation when exposed to concentrated hydrofluoric acid. Analysis by TEM and SEM reveals two attack mechanisms. (1) Poly-Si films deposited onto phosphosilicate glass (PSG) at 605ºC exhibit tensile residual stress and degrade immediately upon exposure to HF, a phenomenon which we attribute to stress-corrosion cracking. Phosphorus from the PSG layer enters the poly-Si during the deposition, resulting in a microstructural gradient which contributes to the cracking mechanism. (2) As-deposited tensile poly-Si films on phosphorus-free LPCVD SiO2 (LTO) and annealed films on LTO and PSG blister at different rates in HF due to penetration at foreign particle inclusion sites and other film defects. Unannealed compressive films deposited at 650ºC onto PSG do not show any evidence of attack.
Fracture Toughness of Silicon and Thin Film Micro-structures by Wedge Indentation
Authors: de Boer M.P. , Huang He , Nelson J.C. , Jiang Z.P. , Gerberich W.W. 
Published: March 2011

ABSTRACTSilicon rooftop structures 30 µm high and of 1 µm linewidth were fabricated in a microelectronics facility using anistropic KOH etching. Aluminum-1% silicon was sputter-deposited to investigate the effects of a ductile thin film on the fracture toughness of a brittle material. The rooftop structures were indented by a Knoop indenter purposely placed off-center so that the indenter was wedge-shaped. Deformation and cracks were photographed by SEM. Crack threshold load per unit width are reported for normal cracks, running perpendicular to the roofline. Fracture toughness is calculated by first order approximation and finite element modeling using SEM measurements of the length of normal cracks. Without a thin film, values for silicon are in reasonable agreement with the literature. With a thin film of only 600 Å, fracture toughness is increased by 45%. Cracks nearly parallel to the roofline also appeared at higher load values. Characteristics of both types of cracks are discussed.
Mechanical Characterization of Diamond-Like Carbon (DLC) Coated Polycarbonates
Authors: Hsieh Alex J. , Huang Paul , Venkataraman Shankar K. , Kohlstedt David L. 
Published: March 2011

ABSTRACTEvaluations of DLC coated polycarbonates have been carried out via high speed projectile impact, three point bend, and continuous microscratch tests. Radial and circumferential microcracks appeared on the back surfaces and near the regions of impact as a result of the high speed impact stresses. Despite the impact, the adhesion of the DLC coating in the area between the cracks remained, except in the immediate vicinity of impact. In the three point bend tests, transverse cracks developed and propagated in the DLC coating when the applied strain reached the fracture limit of the coating. No delamination occurred in the continuous microscratch tests; instead, cracking of the coating was observed in DLC coated polycarbonates. Microcracking was the dominant mode of failure which was consistent in these three diversed mechanical tests. Results of the SEM studies further confirmed microcracking prior to delamination as observed in the high speed impact tested coupons.
Internal Stress Measurement on CVD diamond Coatings by X-ray Diffraction and Raman Spectroscopy
Authors: Van Acker K. , Mohrbacher H. , Blanpain B. , Van Houtte P. , Celis J.P. 
Published: March 2011

ABSTRACTInternal stresses are measured in CVD diamond coatings deposited on a variety of substrate materials by low incident beam angle X-ray diffraction and by micro-Raman spectroscopy. The X-ray diffraction technique gives an integral stress value over a comparably large coating area whereas the Raman technique results in localized stress information with a lateral resolution of down to 1 µm. The stress values obtained from both methods compare well for diamond coatings of 6 μm thickness whereas a difference is observed for thicker coatings.
Mechanical Properties and Residual Stresses in Oxide/Metal Multilayer Films Synthesized by Ion Beam Assisted Deposition
Authors: Kalnas C. E. , Parfitt L. J. , Goldiner M. G. , Was G. S. , Jones J. W. 
Published: March 2011

ABSTRACTFilms of Al, Al2O3 and Al/Al2O3 microlaminates were formed by ion beam assisted deposition (IBAD) at R ratios from 0.0025 to 0.5 and film thicknesses between 150 and 2600 nm. Oxide films were amorphous while metal layers were crystalline with small grains and texture for both PVD and IBAD conditions. The average stress in the oxide film is tensile at R=0 and becomes compressive, saturating at approximately 15 eV/atom. The residual stress in the Al films is tensile over all R ratios and the stress in the microlaminate roughly follows a rule of mixtures. Deformation of ductile substrates on which films had been deposited revealed that the critical strain to fracture was strongly dependent on residual stress. Large compressive stresses in monolithic films produced by ion beam assisted deposition delayed the onset of crack initiation while the presence of multiple layers, in general, lowered the crack density at saturation, suggesting a possible ductilizing effect.
Thermomechanical Behaviour of AgNi Multilayers and Magnetoelastic Effects
Authors: Pelosin V. , Rodmacq B. , Teixeira S.R. , Hillairet J. , Carlotti G. 
Published: March 2011

ABSTRACTThe elastic and anelastic properties of AgNi multilayers prepared by sputtering were investigated during the course of anneal cycles. The respective temperature variations of some of the elastic constants and moduli were followed by Brillouin scattering and dynamical methods based on use of a torsion pendulum and a vibrating-reed system. The last two enabled to investigate the internal damping associated with the presence of two-dimensional defects. It appears that the motion of interfaces and grain boundaries is inhibited by the high defect density. In contrast, substantial effects associated with the motion of the magnetic domain walls were evidenced. Concurrently, internal stresses were studied by in situ deflection measurements. Flow stress values on the order of 1 GPa were observed. Dilatometry experiments showed that a large part of the non-recoverable modifications in the state of stress induced by thermal cycling originates in the densification of the material.
X-ray Analysis of Ni/Ti Multilayers
Authors: Chaudhuri J. , Alyan S.M. , Jankowski A.F. 
Published: March 2011

ABSTRACTThe structure, composition and strain in Ni/Ti multilayers are analyzed using x-ray diffraction theories. The repeat period of the multilayers used in this study ranges from 1.3 to 12.8 nm. The composition modulation is obtained by using a kinematical theory of x-ray diffraction. A sine wave for the shorter repeat period and a rectangular wave for the longer repeat period are predicted for the composition modulation. The strain within each atomic layer is found by iteratively fitting the experimental x-ray diffraction pattern with the simulated one from a dynamical theory of x-ray diffraction. The strain at the interface is tensile in Ni and compressive in Ti with a complete relaxation of the strain at a distance away from the interface.
The Structure and Mechanical Properties of Ru-Cu and Ru-Ti Nanolayer Composites
Authors: Kung H. , Nastasi M. , Jervis T. R. , Hubbard K.M. , Messner R.M. , Mitchell T.E. , Embury J.D. 
Published: March 2011

ABSTRACTMultilayers of Ru-Cu and Ru-Ti have been prepared by electron beam evaporation technique. One set of composites has Ru thickness varying from 250 to 2500Å alternating with Cu or Ti of 15Å. The other set has 250Å of Ru and the Cu or Ti layer varies between 15 and 200Å. Nanoindentation measurements show that there is no significant change in hardness as either Ru or Cu/Ti thickness varies. However, the Ru-Cu multilayer has twice the hardness of the Ru-Ti system. High resolution transmission electron microscopy discloses that there is an epitaxial orientation relationship between Ru and Ti in Ru-Ti while no such relationship exists in Ru-Cu.The strengthening mechanism proposed by Koehler [1] predicts that Ru-Ti composites should have a higher strength than Ru-Cu due to the larger modulus difference between Ru and Ti. The discrepancy between the prediction and the experimental results suggests that other strengthening mechanism(s) may be operating. We have proposed two models based on a "shear" mechanism to explain the differences observed between these two systems. The effects of these mechanisms in controlling the deformation process in nanolayer composites are discussed.
Use of Magneto-Optic Kerr Effect Measurements to Study Strain and Misfit Accommodation in Thin Films of Ni/Cu (100)
Authors: Inglefield H.E. , Ballentine C.A. , Bochi G. , Bogomolov S.S. , O'Handley R.C. , Thompson C.V. 
Published: March 2011

ABSTRACTWe have detected magnetic transitions in Ni/Cu (100) films as a function of Ni thickness through in situ measurements of the magneto-optic Kerr effect (MOKE). Crystalline quality was monitored using in situ RHEED and Auger electron spectroscopy. Films were deposited by molecular beam epitaxy on silicon wafers and cleaved sodium chloride with varying epitaxial Ni layer thicknesses between 10 and 200 A. High-resolution TEM images of these films indicate decreasing misfit dislocation spacing and decreasing strain as measured by moiré fringe analysis with increasing Ni thickness. These observations have been correlated with changes in magnetic anisotropy as measured by MOKE. MOKE, therefore, may provide a tool for in situ monitoring of the kinetics of misfit accommodation in magnetic thin films.
Stress-Temperature Behavior of O3-TEOS Sub-Atmospheric CVD (SACVD) Oxide Films Deposited on Various Oxide Underlayers
Authors: Robles Stuardo A. , Yieh Ellie , Galiano Maria , kwok Kurt , Nguyen Bang C. 
Published: March 2011

ABSTRACTA systematic evaluation of the stress-temperature behavior of O3-TEOS Sub-Atmospheric CVD (SACVD) oxide films used in IMD applications was performed in order to elucidate the surface dependence and mechanical stability of these films when deposited on different oxide underlayers such as PECVD TEOS-based, Silane-based, and thermally grown oxides. SACVD films were deposited at 360°C using different O3:TEOS molar flow ratios. The results obtained in this study indicate that the stress-temperature behavior of SACVD films deposited on PECVD Silane-based and TEOS-based oxides using N2O as the oxidizing agent is similar to that of the SACVD films deposited on silicon. However, a large stress hysteresis is obtained when SACVD films are deposited on PECVD TEOS-O2 and thermally grown oxide underlayers. This large stress hysteresis results from the surface dependence effects of the SACVD oxides on thermally grown and PECVD TEOS-O2 oxide underlayers. Also, this stress hysteresis can be reduced or eliminated by treating the oxide underlayer surface with an in-situ Ar, He, or N2 plasma. Furthermore, it was also found that the SACVD oxides deposited using higher O3:TEOS molar flow ratios are chemically and mechanically more stable.
Elastic Properties of Sputtered Thin Films: Influence of Different Preparation Conditions
Authors: Bottani C.E. , Elena M. , Beghi M. , Ghislotti G. , Guzman L. , Miotello A. , Ossi P.M. 
Published: March 2011

ABSTRACTThis work presents the first results of a study aimed at better understanding the elastic behaviour of hard coatings produced by various techniques. This is important also in view of the need to be able to control the level of internal stresses, particularly in PVD coatings. It is well known that in extreme cases excessive internal stress can lead to complete film destruction. We devote this paper to reactively magnetron sputtered TiN, one of the most widely used compounds. Thin TiN films of different compositions were deposited on Si substrates and characterized by SEM, AES, XRD and Brillouin light scattering.
TEM Investigation of Microwave Joined Si-SiC/Al/Si-SiC and α-SiC/Al/α-SiC.
Authors: Arunajatesan S. , Carim A. H. , Yiin T. Y. , Varadan V. K. 
Published: March 2011

AbstractElectron probe microanalysis (EPMA) and transmission electron microscopy (TEM) have been used to examine the SiC/Al interfaces in microwave joined Si-SiC/Al/Si-SiC and α-SiC/Al/α-SiC. Both the SiC/Al interfaces display intimate contact between the ceramic and metal and are free of porosity. EPMA of the α-SiC/Al/α-SiC joints reveals that no Al has diffused into the bulk α-SiC, unlike the reported diffusion of Al in Si-SiC/Al/Si-SiC. The TEM investigations show that while the Si-SiC/Al/Si-SiC interface is reaction-free, the α-SiC/Al/α-SiC joint contains Si at the interface. The TEM findings are correlated to the strength data available on these joints and the possible reasons for the presence of Si in the absence of Al4C3 in the α-SiC/Al/α-SiC joint are discussed.
Rapid Infrared Joining of Titanium Alloys and Titanium Matrix Composites
Authors: Blue Craig A. , Lin Ray Y. 
Published: March 2011

AbstractA rapid infrared joining (RIJ) technique has been developed at the University of Cincinnati for high temperature materials. This technique takes only a few seconds to a few minutes to join parts up to 1.8 cm in thickness. The advantages of the RIJ technique are quick, simple, inexpensive, no vacuum or pressure needed, no effect on the microstructure of the base material, flexible and feasible for portable operation. For titanium joining, both Ti-6AI-4V and β21S/SCS-6 composite have been successfully joined with infrared at about 1000 °C for 30 seconds in argon with a TiNiCu brazing alloy. The maximum joint shear strength is up to 554 MPa, which is higher than that of any bond joined with conventional brazing techniques. Our study has shown that the longer the joining time, the wider the joining affected zone. Prolonged joining cycles allow for attack of the titanium alloy by the molten brazing alloy. Results from the titanium matrix composite (TMC) joining show that the joining strength for the infrared bonded parts is superior to those processed with the conventional techniques.
Capacitor Discharge and Flash Welding of Sic-Reinforced High Temperature Al Alloys
Authors: Schwartz D. S. , Devletian J. H. , Chen S. J. , Gould J. 
Published: March 2011

AbstractDiscontinuously reinforced Al alloys (DRAs) are difficult to join using conventional fusion welding techniques due to inhomogeneous redistribution of the reinforcements and reaction between molten Al and SiC. Two specialized welding techniques, capacitor discharge welding and flash welding, were assessed as possible ways to avoid these problems. Using these techniques, welds were made with two DRAs: 8009/SiC/llp and 2009/SiC/15w. Capacitor discharge welding resulted in the formation of Al-carbides in the weld zones, but flash welding produced satisfactory joints in both DRAs.
Direct Bonding Method of Aluminum to Stainless Steel by Pressure Casting of Aluminum
Authors: Suganuma Katsuaki 
Published: March 2011

AbstractA new process for joining Al to stainless steel has been established by using pressure casting of Al in air. Blocks of AISI type 304 austenitic stainless steel to be joined were placed in a mold and were preheated at 450 °C – 600 °C in air. Molten Al was poured into the mold and a pressure of 50 MPa was applied immediately. Stainless steel was tightly bonded to Al by the present process. At the optimum preheating condition, the interface strength was higher than that of Al and fracture did not occur at the interface. At the interface, an intermetallic compound layer was formed, and it was analyzed by TEM. Because this process can be carried out in air by casting of Al, the process has a potential for the mass-production of Al/stainless steel joints or clads.
Wafer Bonding for Hybrid Circuit Technology Using Solid-State Reactions
Authors: Ma Z. , Zhou G. L. , Shen T. C. , Lin M. E. , Hsieh K. C. , Allen L. H. , Morkoç H. 
Published: March 2011

AbstractIn this study, we report a new wafer bonding technique for the integration of GaAs- and InP-based optical devices with prefabricated Si electronic devices in hybrid circuit technology. This technique uses a Au-Ge eutectic alloy as the bonding materials between GaAs and Si wafers, and between InP and Si wafers. This process takes advantage of the low temperature solid-state reactions at GaAs/Au-Ge, InP/Au-Ge, and Si/Au-Ge interfaces. The bonding was carried out by annealing the samples at 280–300°C in an alloying furnace. The reliability of the joined wafers was evaluated by both cleavage test and standard thermal cycling test. The joining interfaces were characterized by scanning electron microscopy and transmission electron microscopy. The results reveal that the bonding is achieved by low temperature reactions at the GaAs/Au-Ge and InP/Au-Ge interfaces as well as solid-phase epitaxial regrowth at the Si interfaces. The joined structure has very good integrity.
Microstructural Investigation of κ-Modification Layers in CVD α-Al2 O3/K-Al2 O 3 Multilayer Coatings
Authors: Halvarsson Mats , Vuorinen Sakari , Nordén Hans 
Published: March 2011

AbstractMulti layer alumina coatings consisting of layers of either pure α-A12 O3 or κ-Al2O3, were deposited in a hot wall CVD reactor. In order to nucleate and grow a desired alumina polymorph (α/κ) in each layer, thin α- and κ-modification layers were deposited between the alumina layers. This investigation examines the interfacial structure of the κ-modification and the alumina layers. The materials were examined using a combination of XRD, SEM, TEM and EDX.The κ-modification layers exhibited an FCC structure and were composed of (Ti,AI)(C,O). Orientation relationships were frequently found at the (i) α-A12O3/κ-modification/κ-A12O3 layer interfaces and (ii) κ- A12O3/κ-modification/κ- A12O3 layer interfaces:
Synthesis and Characterization of Metal Silicide/Silicon Carbide Composites by Low Temperature Solid-State Reactions
Authors: Zeng D. , Hampden-Smith M. J. , Wang L.-M. 
Published: March 2011

AbstractCo-reduction of mixtures of MoCl3(THF)3 and SiCls4 in THF using Li/C10H8 or both Li/C10Hs8 and LiBEt3H resulted in formation and separation of black powders which upon thermal annealing at temperatures ranging from 750°C to 1 100°C produced crystalline molybdenum silicide and silicon carbide composite. Co-reduction of mixtures of WCI4 and GeBr4 with LiBEt3H in THF formed W2C and elemental Ge which upon thermal treatment at 750°C for 4 hours generated a small amount of crystalline W5Ge3.