bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic And Structural Properties Of Interfaces Created By Potassium Deposition ON TiO2 (110) Surfaces
Authors: Lad R. J. , Dake L. S. 
Published: March 2011

ABSTRACTPotassium was deposited onto stoichiometric TiO2 (110) surfaces and the chemical bonding and structure were studied with UPS, XPS, LEED, and RHEED. Potassium interacts strongly with the oxygen anions of the TiO2 and reduces the valency of Ti cations at the interface. At submonolayer potassium coverages, a large charge transfer to the substrate causes a sharp drop in work function, a population of electronic states within the bulk TiO2 band gap, and surface band bending. After large potassium doses at 300 K, multilayers of K2O are formed by diffusion of oxygen anions from the substrate, creating a substoichiometric TiO2−x interface composition. No metallic potassium is present even after large doses. The K2O layers remain stable after annealing as high as 900 K, and LEED indicates that they are disordered. RHEED characterization is limited by the roughness of the stoichiometric TiO2 (110) surface.
Analytical Electron Microscopy And High-Resolution Electron Microscopy Studies Of Grain-Boundary Films In Silicon Nitride-Based Ceramics
Authors: Kleebe H.-J. , Rühle M. 
Published: March 2011

ABSTRACTThe microstructures of post-sintered reaction-bonded Si3N4 materials (SRBSN) were investigated. The materials consist of large elongated β-Si3N4 grains embedded in a finegrained matrix. Amorphous secondary phases exist at triple grain junctions owing to the liquid phase sintering involved during densificacition. Those amorphous phases can be crystallized (nearly completely) by post-sintering heat treatment. Apart from these crystalline grain pockets the grains of all materials are covered with thin (<l-2 nm) amorphous intergranular films on both Si3N4/Si3N4 grain boundaries as well as on secondary-phase/Si3N4 phase boundaries. A control of the intergranular films is most desirable since they limit the high-temperature mechanical properties of Si3N4-based ceramics. Therefore, the required characterization was performed by analytical and high-resolution transmission electron microscopy (AEM/HREM). Si3N4 materials with different rare-earth and transition-element oxide additions were studied. AEM and HREM investigations revealed marked differences in thicknesses and chemical compositions of the different intergranular films depending on the system analyzed indicating a strong dependence of film thickness on chemical composition. However, a given composition of each investigated material showed a characteristic intergranular film thickness, independent of grain misorientation, with the only exception of low-energy grain boundaries. The thickness of the intergranular films was constant within 0.2 nm. In addition, the film thickness of phase boundaries was always greater (by 1–2 nm) compared to grain-boundary films.
Stress Effect on Oxidation Kinetics of Silicon with Different Surface Orientations
Authors: Imai Keitaro , Yamabe Kikuo 
Published: March 2011

ABSTRACTThermal oxidation of different crystallographic surface orientations of Si reveals a complex rate behavior not only in the initial stage but also in sequential two step oxidation with high temperature annealing where enhanced oxidation is observed as well. These phenomena are explained by the reduction of oxygen solubility in SiO2 due to stress in the SiO2 film, which has been confirmed by isotope labeling oxidation with SIMS analysis.
An Anodic Process for the Determination of Grain Boundary and Film Thickness Strengthening Effects in Aluminum Films on Oxidized Silicon.
Authors: Venkatraman Ramnath , Bravman John C. 
Published: March 2011

ABSTRACTWe have measured stress variations with temperature as a function of film thickness and a given grain size in pure Al and AI-0.5%Cu films on Si substrates. The variation in thickness for a given grain size is brought about by using the same film and the repeated controlled growth and dissolution of a barrier anodic oxide which can be grown uniformly on the film. Stress measurements were made as a function of temperature by measuring wafer curvature after successively removing each 0. Iμm of Al film. The components of strengthening due to the film thickness and the presence of grain boundaries were separated by assuming that the flow stress of the film is simply the sum of these two components. The observations are consistent with results obtained using lascr-rcflowed films in an earlier work. The variations of these two components with temperature, and under tension and compression is discussed.
Evolution of Intrinsic Stress During Nucleation and Growth of Polycrystalline Tungsten Films by Chemical Vapor Deposition.
Authors: Leusink G. J. , Oosterlaken T. G. M. , Janssen G. C. A. M. , Radelaar S. 
Published: March 2011

AbstractWe present in situ measurements of the intrinsic (growth) stress during nucleation and growth of thin tungsten films by chemical vapor deposition. It is shown that interfering stress sources, as recrystallization or plasic flow, do not contribute to the intrinsic stress in these films. This makes W-CVD a model system for the experimental study of the relation between the evolution of microstructure and the development ofgrowth stress.
Structure and Dose Effects on Ion Beam Modification of Polymers
Authors: Rao G. R. , Lee E. H. , Mansur L. K. 
Published: March 2011

ABSTRACTPolyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethersulfone (PES) were implanted with 200 keV boron ions at three different doses. PS was also implanted with 100 keV boron. A nanoindentation technique and reciprocating sliding wear tests were used to characterize mechanical properties of the implanted polymers. The results showed that hardness increased with increasing dose as well as increasing energy. The percentage increase in hardness was reduced with increasing complexity of the side groups although absolute hardness values were higher. With increasing complexity of the main backbone, polymer chain, the percentage increase in hardness as well as numerical hardness values were lower. These effects were attributed to the relative contributions of cross-linking and chain scission which were viewed as competing processes. Wear tests showed that in general, a lower or intermediate implant dose yielded the best improvement in wear resistance. No specific trends were observed for relating friction coefficient values and improved wear resistance. The results indicate that wear is a complex phenomenon which has a sensitive dependence on hardness and elastic properties of the mating surfaces.
Determination of Strain Distributions in Aluminum Thin Films as a Function of Temperature by the use of Synchrotron Grazing Incidence X-Ray Scattering
Authors: Venkatraman Ramnath , Besser Paul R. , Brennan Sean , Bravman John C. 
Published: March 2011

ABSTRACTWe have measured elastic strain distributions with depth as a function of temperature in Al thin films of various thicknesses on oxidized silicon using synchrotron grazing incidence X-ray scattering (GIXS). Disregarding minor surface relaxation effects that depend on the film thickness, it is shown that there are no gross strain gradients in these films in the range of temperatures (between room temperature and 400°C) considered. We also observe X-ray line broadening effects, suggesting an accumulation of dislocations on cooling the films, and their annealing out as the films are reheated.
Calculation of Stress Gradients in Thin Al-0.5%Cu/Ti Lines from Strain Gradients Measured as a Function of Temperature Using Grazing Incidence X-Ray Scattering
Authors: Besser Paul , Venkatraman Ramnath , Brennen Sean , Bravman John 
Published: March 2011

ABSTRACTStrain gradients in Al-0.5%Cu lines on a 1000Å Ti barrier layer have been measured during thermal cycling from room temperature to 400°C using X-rays from a Synchrotron Source in the Crazing Incidence Geometry. The stress gradient calculated from the strain gradient is shown at four temperatures during thermal cycling. The surface of the line is relaxed relative to the bulk during heating and more stressed during cooling. It was also found that the width direction of the line supports essentially no stress throughout the thermal cycle and that the much of the stress along the length of the line is relaxed during the first few minutes at elevated temperatures.
Effect of Initial Substrate Curvature on Nonlinear Bending Measurements of Thin-Film Stress.
Authors: Fahnline D. E. 
Published: March 2011

ABSTRACTA recently reported nonlinear model of the bending of a thin-film/substrate bilayer provides a means for determining stress in thin films even for large deflection and ellipsoidal bending. This model replaces the usual Stoney's equation, which is valid only for small deflections. However, the model omits consideration of the commonly observed initial curvature of the substrate before deposition. In the small deflection regime the principle of superposition justifies simply subtracting the initial curvature from the final curvature after deposition, but for large deflections this is inappropriate, because the principle of superposition is no longer valid. The present paper presents a modified form of the nonlinear model incorporating initial substrate bending. The resulting equations show that initial substrate curvature causes magnified nonlinear effects and provide a means for determining film and substrate elastic properties in addition to thin-film stress.
Influence of Adsorbate Monolayer on the Nano-Mechanics of TIP-Substrate Interactions
Authors: Rafii-Tabar H. , Pethica J. B. , Sutton A. P. 
Published: March 2011

ABSTRACTWe employ constant temperature molecular dynamics simulations to study, at the atomistic level, the interactions of an Ir tip with a Pb substrate. We have considered the complete cycle of approach.contact, indentation and retraction of the tip from the substrate. We have observed the wetting of the tip by the substrate atoms, and the formation of atomic necking between the tip and the substrate.We have carried out further simulations to study the interactions of an Ir tip with an Ir substrate covered with an adsorbate monolayer of Pb film. We show that the introduction of the adsorbate considerably reduces the work of adhesion and the extent of plastic flow, in agreement with experimental results.Three-dimensional geometries have been generated on computer and used for the animation of the simulation runs.
Acoustic Emissions During Indentation Tests
Authors: Weihs T P , Lawrence C W , Derby B , Scruby C B , Pethica J B 
Published: March 2011

ABSTRACTWhen a hard tip indents a sample, cracking, delamination and plasticity can all produce acoustic signals in the form of elastic waves. This paper describes how these acoustic emissions (AE) can be monitored using piezoelectric elements and a load-controlled indentation instrument. Signals emitted from thin films and bulk materials are shown and they are correlated with distinct jumps in displacement of the indenter tip. The benefits and difficulties of different methods of monitoring the emissions are also considered.
Relaxation in Sub-Micron Si-1-xGex Strain-Layer Mesas
Authors: Luo Dawei , Howard David J. , Paine David C. 
Published: March 2011

ABSTRACTFinite element modelling of strain-layer mesa structures shows that edge effects can contribute to the relaxation of in-plane misfit stress. Calculations were performed for a 200 nm thick layer of Si90Ge10 grown epitaxially on an <001> Si substrate which was patterned into 400-nm-high mesas ranging in diameter from 0.6 to 7 μm. These calculations were experimentally investigated using plan-view TEM to study relaxation in patterned and unpatterned material. This composition and film thickness exceeds the critical thickness predicted using simple strain energy considerations. In one experiment, an initially defect-free 200-nm-thick Si90Ge10 layer was annealed at 960°C for 1 hr to create a nearly fully relaxed layer which was then lithographically patterned into an array of sub-micron mesas. The wafer was then annealed for a second time and changes in the character of die pre-existing dislocations were studied.
Stress and Microstructure in Rf-Diode and Dc-Magnetron Sputtered Beryllium Thin Films
Authors: Mutikainen Risto H. 
Published: March 2011

ABSTRACTThe effect of deposition parameters on the properties of sputtered Be films has been studied. The parameters have been optimized to obtain stress free films. Nitrogen pulsing has been used to improve the film microstructure by suppressing the columnar grain growth.
Thermal Degradation of SiGe Interfaces Studied by X-Ray Reflectivity and Diffraction
Authors: Hudson J. M. , Powell A. R. , Bowen D. K. , Wormington M. , Tanner B. K. , Kubiak R. A. , Parker E.H.C. 
Published: March 2011

ABSTRACTWe demonstrate the use of x-ray diffraction to provide accurate compositional information, together with grazing incidence reflectivity to provide information on layer thicknesses and surface and interface roughnesses, on Si/Si1-xGex superlattice structures of less than 200nm total thickness.The quality of SiGe interfaces has been investigated in superlattices where x varies from 0.1 to 0.5. At low Ge compositions the interfaces are shown to be smooth to a few angstroms. However, as the Ge composition in the SiGe layer approaches 50%, severe roughness is observed at the SiGe to Si interfaces, although the Si to SiGe interfaces remain relatively smooth.Upon annealing for one hour at 850°C the Ge diffuses outwards from the SiGe layers and can be closely modelled by inclusion of a (2.4±0.3)nm linearly graded layer either side of the SiGe layer into a simulation program. The long range roughness at the SiGe to Si interface is lost upon annealing leaving only a short range roughness of similar size to the Si to SiGe interface roughness.Reflectivity measurements have been shown to distinguish between interface roughness and interdiffusion for the annealed system.
Nanometer-Scale Modification and Imaging of Polyimide Films by Scanning Force Microscopy
Authors: Unertl W. N. , Jin X. 
Published: March 2011

ABSTRACTThe sharp tip of a scanning force microscope can be used to make controlled modifications of polymer surfaces. In this paper, we describe the properties of micrometer size pits up to 900 Å deep formed on Kapton-H surfaces. The structure at the bottom of the pits appears to be closely related to the degree of crystallinity near the surface. We also use elasticity theory to estimate that the resolution of scanning force microscopy for polymer surfaces is about 160 Å for tips with 400 Å radius. This estimate agrees well with the resolution obtained in images of polyimide surfaces.
Thin Film Adhesion Study in Microelectronic Packaging
Authors: Jeong H. S. , Chu Y. Z. , Freiler M. B. , Durning C. , White R. C. 
Published: March 2011

ABSTRACTFracture energy (Ga) of BPDA-PDA polyimide (PI) on modified and unmodified Si surfaces was measured by the “blister” test as a function of final cure temperature. It is proven quantitatively that surface modification prior to thin film deposition enhances adhesion. Metal adhesion to PI was also measured by the same method. Reproducibility of the data was found to be exceptionally good for both cases. The linear elastic model is quite valid for the test of thin film adhesion. Therefore, it is believed that this test is best suited for Ga measurements in the study of thin film adhesion for microelectronic packaging.
Cracking and Adhesion of Ceramic Films
Authors: Atkinson Alan , Guppy Richard M. 
Published: March 2011

ABSTRACTBrittle films of ceramics on metal substrates become mechanically unstable when a critical thickness is exceeded. Experiments have been carried out to investigate this instability for films under tension and compression. Films of cerium oxide gel under tension were prepared by spin-coating a ceria sol onto stainless steel substrates. Films exceeding a critical thickness failed by through-film cracking. The relationship between crack spacing and film thickness was consistent with partial interfacial delamination accompanying film cracking. Films of nickel oxide under compression were prepared by the oxidation of nickel and NiAl and NiCr alloys. The adhesion of the films to the substrates was measured in a double bending beam configuration and by scratch testing. A critical thickness was observed at which adhesion became very low and which depended on the composition of the metal substrate. The observed behaviour is consistent with a buckling instability in the film. In both types of film the conditions for crack propagation appear to determine instability, but the nature of the failure-initiating defects remains obscure.
The Origin of Anomalous Strain in Thin Sputtered Mo Films on Si(100)
Authors: Tao J. , Adams D. , Yalisove S. M. , Bilello J. C. 
Published: March 2011

ABSTRACTStress and structure evolution in thin films of sputtered Mo on Si(100) substrates has been studied, as a function of microstructure, by x-ray diffraction, transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy (RBS). Double crystal x-ray diffraction topography (DCDT) has been employed to determine film stress as a function of thickness. High compressive stress, about 1000 MPa, is found for the thinnest Mo film. With increasing film thickness a minimal residual stress level is reached. Low incidence angle x-ray diffraction patterns indicated that crystalline Mo is present even in the thinnest films. Line broadening of the Mo(l10) diffraction peak has shown that the grain dimension is comparable to the film thickness over the range studied. Plan view TEM observations of films less than 20nm demonstrated the presence of continuous film with grain dimensions on the order of film thickness, in good agreement with the x-ray results.
Frictional Effects in the Buckling Delamination of a Compressed Thin Film and Implications for Interfacial Fracture
Authors: Stringfellow R. G. , Freund L. B. 
Published: March 2011

ABSTRACTAs a film in residual compression delaminates from a substrate, the post-buckling response of the film tends to drive it into the substrate in the region directly behind the delamination front. We consider the process of frictional interaction between the film and the substrate during the delamination process in order to assess the effect of Coulomb friction on the energy release rate, G, driving the delamination. For the case in which the film and the substrate have identical elastic properties, we derive a singular integral equation to determine the relative sliding displacement of the opposing faces of the interface. Using an analytical model, we find that G decreases by about 35% when the coefficient of interfacial friction is equal to one. Using finite element methods, we then investigate the effects of compliance differences between the film and the substrate. We find that, when the film is more compliant than the substrate, frictional interaction is enhanced and the calculated energy release rate decreases substantially. We conclude that frictional effects can account for a significant portion of the energy dissipation during the delamination process, and thus can play an important role in the observed arrest of spreading delaminations.
Continuous Microindentation and Microscratch Measurements of Metal-Ceramic Adhesive strengths
Authors: Venkataraman S. , Kohlstedt D. L. , Gerberich W. W. 
Published: March 2011

ABSTRACTTo investigate the effect of heat-treatment on the adhesion of Pt thin films to NiO substrates, the strain energy release rate, interfacial fracture toughness and interfacial shear strength were determined from continuous microscratch and continuous microindentation experiments. Samples were prepared by sputtering Pt onto single crystals of NiO, followed by a heat-treatment at temperatures of 300, 500 and 800°C and an oxygen partial pressure of either 0.21 or 10-5 atm. Continuous microscratch tests were performed by driving a conical indenter with either a 1 or 5 μm tip radius simultaneously into and across the Pt film. From the magnitude of the critical load at the point of film delamination and the area of the delaminated piece of the thin film, the strain energy release rate (practical work of adhesion) and interfacial fracture toughness were calculated. The practical work of adhesion and interfacial fracture toughness increased from 0.2 J/m2 and 0.2 MPa√m, respectively, for as-sputtered samples to 4.6 J/m2 and 1 MPa√m for samples heat-treated at 500°C and 10-5 atm. Preliminary analysis of continuous microindentation results for Pt/NiO samples yielded interfacial shear strengths of 270 MPa for as-sputtered samples and 725 MPa for samples heat-treated at 500°C and 10-5 atm. While these values are in good agreement with those determined by other methods for metal-ceramic systems, there are sufficient differences in test method for a single system to require additional analysis of the proposed models.
Improvement of Tribological Properties of Mosa Films by Forming Interlayers and/ or Bombarding with Ions
Authors: Matsui Akihiko , Kagimoto Yoshimi 
Published: March 2011

ABSTRACTThe effects of forming interlayers and/or bombarding with ions on the tribological properties of the sputter-deposited MoS2 films were investigated. The MoS2 films on substrates of Ti-alloy, martensitic stainless steel and high speed tool steel with TIN interlayers were evaluated by ball/disk sliding tests under ultra-high vacuum condition. Furthermore, nitrogen- or sulfer-ion-bombarded MoS2 films tested too. The test results showed correlation between the surface hardness of substrates and the wear life of MoS2 films. The wear life of the ion-bombarded MoS2 films was improved by mixing film/substrate interface.
Effect of High Temperature Stress on Titanium-Tungsten Gold thin Films on Alumina
Authors: Koh Wei H. , Louie W. 
Published: March 2011

ABSTRACTThe adhesion of a sputtered titanium-tungsten gold (Ti-W/Au) thin film on alumina substrates is found to be weakened after being stressed at temperatures above 575°C, due to depletion of the Ti-W base metal. Thin films deposited on substrates having a fine grain structure and as fired surfaces, however, maintained their adherence at temperatures up to 650°C.
Adhesion and Tribological Properties of Ag and Ag/Ti Films on Zro2 Ceramic Substrates After Heat Treatment at 250°C
Authors: Hsieh J. H. , Ajayi O. O. , Erdemir A. , Nichols F. A. 
Published: March 2011

ABSTRACTAg and Ag/Ti films were deposited on ZrO2 substrates by ion-beam-assisted deposition. Adhesion of these films was measured before and after heat treatment at 250°C in air. The results show that a graded interface between Ag and Ti was necessary for the Ag films to survive the heat treatment. Reciprocating pin-on-disc tests were performed at 150°C after heat treatment to investigate the relationship between adhesion and tribological properties. The failure of Ag and Ag/Ti (without graded interface) films was also observed during wear tests. However, this Ag film failure did not result in negative effects. All three Ag-coated substrates show better tribological behavior.
Electromigration Resistance and Mechanical Strength: New Perspectives for Interconnect Materials?
Authors: Arzt E. , Kraft O. , Sanchez J. , Bader S. , Nix W. D. 
Published: March 2011

ABSTRACTA brief review is given of models which propose a correlation between electromigration resistance and the mechanical strength of thin film interconnects. In an attempt to achieve metallurgical strengthening and improved electromigration resistance, aluminum films were implanted with oxygen ions. Preliminary electromigration tests on line arrays patterned from these films resulted in lifetimes comparable to the standard Al films. The lack of improvement is attributed to enhanced hillock/whisker growth during electromigration in the implanted interconnects. This behavior is coincident with a lower compressive strength in similarly treated continuous films at elevated temperatures as measured by the substrate curvature technique.