bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Mechanical Properties of Electroplated Cu Thin Films Measured by means of the Bulge Test Technique
Authors: Xiang Yong , Chen Xi , Vlassak Joost J. 
Published: April 2011

ABSTRACTThe mechanical properties of freestanding electroplated Cu films were determined by measuring the deflection of Si-framed, pressurized membranes. The films were deformed under plane-strain conditions. The pressure-deflection data are converted into stress-strain curves by means of simple analytical formulae. The microstructure of the Cu films was characterized using scanning electron microscopy and x-ray diffraction. The yield stress, Young's modulus, and residual stress were determined as a function of film thickness and microstructure. Both yield stress and Young's modulus increase with decreasing film thickness and correlate well with changes in the microstructure and texture of the films.
Effect of Microstructure on Microhardness of AlN Thin Films
Authors: Miyabe Shuichi , Aono Masami , Kitazawa Nobuaki , Watanabe Yoshihisa 
Published: April 2011

ABSTRACTAluminum nitride (AlN) thin films with columnar and granular structures were prepared by ion-beam assisted deposition method by changing nitrogen ion beam energy, and the effects of the film microstructure and film thickness on their microhardness were studied by using a nano-indentation system with the maximum force of 3 mN. For the columnar structure film of 600 nm in thickness, the microhardness is found to be approximately 24 GPa when the normalized penetration depth to the film thickness is about 0.1. For the granular structure film of 700 nm in thickness, the microhardness is found to be approximately 14 GPa. These results reveal that the microhardness of the AlN films strongly depends on the film microstructure, which can be controlled by regulating the nitrogen ion beam energy.
Mechanics of Indium-Tin-Oxide Films on Polymer Substrates with Organic Buffer Layer
Authors: Park Sung Kyu , Han Jeong In , Kim Won Keun 
Published: April 2011

ABSTRACTThis study was undertaken to derive the understandings of the electro- mechanical properties of ITO films on highly elongated polymer substrates which were subjected to thermally and mechanically stresses. The substrates are polycarbonate foils with 100, 180 and 200-mm thicknesses with gas barrier layer on their bottom surface. The metallic films used in the experiments are indium- tin-oxide (ITO) and tantalum (Ta) films. Strain- gauge measurements and numerical analyses using modified Stoney formula were carried out to determine the electro-mechanics in ITO films. The numerical analyses and empirical results show the thermally and externally induced mechanical stresses in ITO films on polymer substrates are responsible for the difference in thermal expansion between the ITO films and the substrate and for substrate material and thickness, respectively. Therefore, a ramped heating processing and a buffer layer were employed to improve the electro- mechanics, and then, the effects of the buffer layer were also quantified in terms of conductivity-strain variations.
Nanoindentation Induced Fracture in Hard Multilayer Thin Films
Authors: Karimi A. , Bethmont D. , Wang Y. 
Published: April 2011

ABSTRACTDepth sensing nanoindentation and nanoscratch testing were combined with atomic force microscopy (AFM) and electron microscopy observations to study mechanical properties and fracture behavior of a number of TixAl1-xNyC1-y hard thin films. Various failure modes were activated either by normal loading-unloading or by microscratching of the samples to provide an estimation of the fracture toughness and interfacial fracture energies. By changing chemical composition and deposition conditions various nanostructured thin films including monolitically grown single layer, nanocomposite, and multilayers were coated onto the tungsten carbide-cobalt substrates. All tested films exhibit elevated mechanical properties with high hardness (38 – 45 GPa) and modulus (500 – 570 GPa). Under sufficiently high load indentation the formation of corner Palmqvist type radial cracks were usually observed because of small modulus mismatch between coating and substrate, good adhesion, and in particular high toughness of both substrate and films in spite of great difference in their respective hardness. Various failure modes were activated and the sequences of fracture events were determined using stepwise or continuously increasing load scratch tests. Some other films were found to be more sensitive to tensile stress behind the indenter which generates regularly repeated microcracks on the scratch track. Other films in particular multilayers were appeared more susceptible to compressive stress ahead of the indenter leading to local delamination at the interface between layers and the formation of irregular microcracks under the contact zone.
Multiple Cracks of a Thin Film on a Ductile Substrate
Authors: Zhao Ming-Hao , Fu Ran , Zhang Tong-Yi 
Published: April 2011

ABSTRACTThe present work proposes a Dugdale type model to theoretically predict the multiple cracks of a residually tensile stressed thin film on a ductile substrate. The results show that there exists a critical value, Rc, of the cracking resistance number, R. When R < R, the film > c cracks and the normalized crack spacing is determined by cracking resistance number and the stress ratio of the residual stress to the yield strength of the substrate.
Stress Development and Adhesion Behavior in Thin Ceramic Coatings Monitored by Positron Annihilation During Bending
Authors: Galindo R. Escobar , Veen A. van , Schut H. , Carvalho N.J.M. , Strondl C. , Hosson J. Th. M. de 
Published: April 2011

ABSTRACTPositron Beam Analysis was for the first time performed in combination with a four-point bending stage. Applications of this novel technique on PVD TiN (5 m thick), WC:H (2.5 m) and CrN (1.5 m m) layers on tool steel, low carbon steel and stainless steel substrates are discussed. It appeared from PBA results that for these systems the coatings did not fail by delamination during bending. SEM confirmed that there was no decohesion but instead, cracking of the coatings was observed. In order to weaken the interface and quantify adhesion properties we propose to induce blistering based on localised gas implantation.
The Role of Chemical Composition for the Ductility and Microstructure of Thin NiAl Films
Authors: Wellner Patrick , Kraft Oliver , Arzt Eduard 
Published: April 2011

ABSTRACTIn this work, NiAl films deposited by magnetron co-sputtering onto silicon substrates with compositions between 45.0 and 51.5 at-% Al and a thickness of 1.2 μm were studied. The films exhibited grain sizes comparable to the film thickness. Furthermore, the films were found to have fiber textures with the strongest component being (110) for the very Ni-rich and (111) for the stoichiometric and Al-rich films. The residual stresses in the Ni-rich and stoichiometric films after annealing were found to be independent of composition, while the Al-rich films showed a significant decrease in film stress. This stress drop can be related to severe cracking in the Al-rich films, which has not been observed in the stoichiometric and Ni-rich films, indicating that the fracture toughness depends on composition. Based on a simple estimate, the fracture toughness of these Al-rich films was determined to be in the range of 1 to 2 MPa m-1/2, which is somewhat smaller than commonly reported bulk values for polycrystalline NiAl.
Atomistic Simulations of Deposition Processes of Epitaxial Layers
Authors: Shintani K. , Sugii H. , Nishimura M. , Nakajima T. 
Published: April 2011

AbstractThe deposition process of epitaxial layers is simulated by the method of molecular dynamics. The interaction forces between atoms are calculated using the Stillinger-Weber potential. Before the deposition of atoms, the substrate is equilibrated at a specified temperature. Atoms with identical initial velocities and with initial coordinates selected at random in the plane parallel to the growth surface arrive at the substrate to form an overlayer. During the deposition, the lower part of the substrate is held at an initially specified temperature by velocity scaling. How the growth morphology of an overlayer is influenced by the substrate temperature is investigated in connection with the behavior of deposited atoms.
STM analysis of copper thin films using hyperthermal copper ions
Authors: Pomeroy J.M. , Cooper B.H. , Brock J.D. 
Published: April 2011

AbstractSTM analysis of thin copper films grown on Cu(111) and Cu(100) at room temperature using hyperthermal ions reveals several morphological features not present in thermally grown films. Hyperthermal deposition of thin films has become a popular industrial technique due to observed decreases in film roughness and stress with increased grain sizes, but the link between incidence energy and these properties is poorly understood. Using a sophisticated molecular dynamics (MD) simulation, morphologies observed in experimentally grown films are correlated with the activation of hyperthermal atomistic mechanisms in the MD. Previous work has provided strong evidence for activation of adatom-vacancy pair production near 20 eV on Cu(111). Evidence will be presented here for the activation of sputter erosion near 40 eV. A proposal for quantifying the effect of energy on nucleation density by modifying the flux term in mean field nucleation theory will be presented. Other processes which directly contribute to smooth growth, such as atomic insertion near 10eV, have been proposed but are more difficult to correlate with the data due to their subtle morphological signatures.
GaAs Heteroepitaxy on Fluoride by Electron Beam Induced Surface Modification
Authors: Fritz Tobias , Haiml Markus , Schön Silke , Keller Ursula 
Published: April 2011

AbstractGaAs saturable absorber materials are used in ultrafast nonlinear optics to obtain all-optical switching in optoelectronic devices. They are introduced to semiconductor saturable absorber mirrors (SESAMs) for the generation of ultrashort laser pulses. GaAs is grown on CaF2 by molecular beam epitaxy to fabricate devices, which provide a large high reflection bandwidth. The CaF2 surface was exposed to high- and low-energy electron irradiation before and during growth to increase the surface free energy for the subsequent GaAs overgrowth. A three-layer GaAs/ fluoride device was designed and fabricated to study the impact of the electron exposure on the growth mode and the surface roughness. The surface morphology of an optoelectronic device can cause nonsaturable losses, which degrade the device performance. Therefore, the effect of the electron exposure of the CaF2 layer on the surface roughness of the device was studied by atomic force microscopy. Measurements of the scattered light from the device surface allowed for a quantitative analysis of the nonsaturable losses attributed to the surface morphology of the device.
Stress origin and relaxation in epitaxial AlN thin films on SiC
Authors: Bathe Ravi , Vispute R.D. , Habersat Daniel , Sharma R. P. , Venkatesan T. , Scozzie C. J. , Ervin M. H. , Jones Ken 
Published: April 2011

AbstractWe have investigated the epitaxy, surfaces, interfaces, and defects in AlN thin films grown on SiC by pulsed laser deposition. The stress origin, evolution, and relaxation in these films is reported. The crystalline structure and surface morphology of the epitaxially grown AlN thin films on SiC (0001) substrates have been studied using x-ray diffraction (θ–2θ, ω, and Ψ scans) and atomic force microscopy, respectively. The defect analysis has been carried out by using Rutherford backscattering spectrometry and ion channeling technique. The films were grown at various substrate temperatures ranging from room temperature to 1100 °C. X-ray diffraction measurements show highly oriented AlN films when grown at temperatures of 750- 800 °C, and single crystals above 800 °C. The films grown in the temperature range of 950 °C to 1000 °C have been found to be highly strained, whereas the films grown above 1000 °C were found to be cracked along the crystallographic axes. The results of stress as a function of growth temperature, thermal mismatch, growth mode, and buffer layer thickness will be presented, and the implications of these results for wide band gap power electronics will be discussed.
Surface reconstruction and induced uniaxial magnetic fields on Ni films
Authors: Lukaszew R. A. , McNaughton B. , Stoica V. , Clarke R. 
Published: April 2011

AbstractMetal ceramic interfaces are important in applications as diverse as magnetic storage media to support catalysts. Understanding the correlation between the films structure and its properties is very important for applications. For example the lattice mismatch between substrate and epilayer during heteroepitaxial growth induces strain as well as defects on the structure of the films that in turn affect the magnetic properties.We have previously shown that it is possible to obtain epitaxial (001) and (111) Ni films grown on MgO substrates. [1] In particular we observed that the crystalline quality of the films improved considerably after 10 nm of film growth and annealing of the films indicated significant reduction of the surface roughness. In addition, after annealing (001) Ni films we observed nano-patterning of the surface through self-assembly of periodic “stripes”.We will now present our analysis of the magnetic properties of these films, in particular the azimuthal dependence of the magnetization reversal, using MOKE, and we will attempt to correlate our findings with the surface characterization obtained with STM.
Morphologies of Self-Assembled Quantum Dots: A Variational Approach
Authors: Budiman R. Arief , Ruda Harry E. 
Published: April 2011

AbstractWe construct a 3D model for coherent island formation by (i) using a novel 3D strain tensor to account for bulk strains and (ii) representing adatom di.usion as an external field that perturbs an otherwise. at strained layer. Equilibrium shapes of coherent islands and wetting layer thickness are obtained. Coherently compressed layers are typically unstable, but become stable in tension. Comparisons with Si1-xGex/Si(001) and Si0.5Ge0.5/Si1-xGex(001) layers are discussed.
Growth and characterization of Ge nanostructures on Si(111)
Authors: Rosei F. , Motta N. , Sgarlata A. , Balzarotti A. 
Published: April 2011

AbstractScanning Probe Microscopy (SPM) in situ is used to study the evolution of Ge islands grown by Physical Vapor Deposition on Si(111) 7×7 reconstructed surfaces. Large 3D islands form on the Wetting Layer (WL), with average lateral dimension in the range 200 - 500 nm. The statistical distribution of the island shapes has been analyzed, showing that three types of shapes coexist under certain conditions: strained, partially relaxed and ripened (atoll-like) islands. We measured the contact angles of the island facets, and observed the depletion of the substrate around the ripened islands. These features are attributed to the misfit strain, which is partially relieved by interdiffusion of Si into the Ge layers.
Interface Engineering in Type-II CdSe/BeTe Quantum Dots
Authors: Ivanov Sergey V. , Shubina Tatiana V. , Sorokin Sergey V. , Toropov Alexey A. , Kyutt Reginald N. , Sitnikova Alla A. , Willander Magnus , Waag Andreas , Landwehr Gotfried 
Published: April 2011

AbstractStressor-controlled epitaxy has been proposed as an efficient method of CdSe quantum dot fabrication. The studies are performed on a type-II CdSe/BeTe system, where CdTe and BeSe inteface bonds play a role of intrinsic stressors. Predeposition of ~0.2 ML CdTe stressor ( Δ a/a= +15%), corresponding to a local maximum of RHEED specular spot intensity, appears to induce variation of stress field across the BeTe surface, caused by alternating regions with CdTe and BeSe bonds. It results in preferential nucleation of regularly arranged CdSe QDs at the BeSe sites with the following vertical chess-ordering in the CdSe/BeTe multilayers. The structures demonstrate bright up to RT PL in the 1.9-2.1 eV range and strong in-plane PL anisotropy related to non-equivalent bottom and top CdSe QD interfaces having estimated from x-ray diffraction total concentrations of CdTe and BeSe bonds of 0.3-0.4 and 0.6-0.7 ML, respectively.
Optical Characterization Of Self-Assembled Ge Dots On Silicon
Authors: Marabelli F. , Rastelli A. , Valsesia A. , Känel H.von 
Published: April 2011

AbstractSelf assembled quantum dots of Ge were obtained by magnetron sputter epitaxy of seven monolayers of Ge on a 33nm thick undoped Si buffer grown on top of a p-doped (100) Si substrate. The samples obtained in this manner were then capped with an increasing number of silicon layers in order to study the effect of Si deposition on the strain and the morphology of the dots. They were characterized “ex situ” by spectroscopic ellipsometry and Raman spectroscopy. The optical experiments revealed well defined differences between the capped and uncapped samples and among samples with different cap thicknesses.By monitoring the energy and the splitting of the E0', E1 and E2 interband optical transitions of Ge and the Ge-Si vibrational mode, the optical measurements evidence strain effects as well as the formation of SiGe alloy, in agreement with the ``in situ'' STM measurements.
Stress relaxation during two-dimensional pseudomorphic epitaxial growth of metals
Authors: Andrieu Stéphane , Turban Pascal , Lapena Laurent , Muller Pierre 
Published: April 2011

AbstractThe analysis of RHEED diffraction peaks during two-dimensional (2D) pseudomorphic epitaxial growth leads to the well known RHEED oscillations but also to diffraction peak width and in-plane lattice spacing oscillations. These behaviors are evidenced in several metallic A/B systems in this paper. As in-plane lattice spacing oscillations are assumed to be due to elastic relaxation at the edge of the 2D Islands, we try to correlate the amplitude of the detected effect with the misfit. The width oscillations are assumed to be due to the scattering coming from islands. We actually show that the full width at half maximum (FWHM) at half coverage allows us to get a correct estimation of the nucleation density. We thus show experimentally that the in-plane lattice spacing oscillations amplitude depends on the nucleation density determined using FWHM measurements. Finally, a theoretical justification allows us to show that this amplitude also depends on the Young modulus ratio of both B and A layers.
Plume and Jetting Regimes in a Laser Based Forward Transfer Process as Observed by Time-Resolved Optical Microscopy
Authors: Young D. , Auyeung R. C. Y. , Piqué A. , Chrisey D. B. , Denham H. , Dlott Dana D. 
Published: April 2011

ABSTRACTMatrix-Assisted Pulsed Laser Evaporation Direct-Write was investigated by ultra high-speed optical microscopy. A layer of viscous fluid was irradiated with 355nm, 30 ns laser pulses in a laser-forward transfer configuration. The fluid response as a function of fluence was studied, and several distinct regimes of behavior were observed: plume, jetting and sub-threshold. However, the transition between plume and jetting regimes was not readily evident in a study of transfer pixel area vs. fluence, which may be explained by material-substrate interactions.
Direct Ink Jet Printing of Alumina Components
Authors: Ainsley C. , Reis N. , Derby B. 
Published: April 2011

ABSTRACTAlumina slurries containing up to 40% by volume ceramic particles suspended in alkane waxes have been developed with viscosity sufficiently low to allow direct ink-jet printing. Components fabricated by printing have been dewaxed, sintered and shrinkage and density measured. Small differences in shrinkage have been measured parallel and perpendicular to the droplet motion but these are within experimental scatter. The manufacturing process appears to generate bands of slightly larger grain size material at the interface between deposited layers.
Analysis of Drop-on-Demand Ink Jet Print Head for Rapid Prototyping
Authors: Shin Dong-Youn , Grassia Paul , Derby Brian 
Published: April 2011

ABSTRACTThe rapid prototyping industry is growing dramatically because of its high potential to reduce product design and prototyping cycles. One of the recent technologies in this field is 3D printing using conventional ink jet technology. In order to maximize the capability of this process, it is required to understand the operating mechanism and drop formation process. The current work focuses on the mechanism of a piezoelectric cylindrical actuator and the hydrodynamic characteristics inside a print head in order to achieve more realistic boundary conditions for the numerical simulation of the drop formation process. Linearised Navier-Stokes equations for Newtonian fluid flow are solved analytically for the pump section with a constant radius and for the nozzle section with a tapering angle. Results from the developed solutions are input to Flow 3D and it is observed that analytical pressure histories show better agreement with numerical results than axial velocity histories. The presented analytic model can be used for fully further drop formation simulation as an upstream pressure boundary within an acceptable tolerance.
An ab initio Investigation on the Effects of Impurity in Aluminum Grain Boundary
Authors: Lu Guang-Hong , Tamura Tomoyuki , Kamiko Masao , Kohyama Masanori , Yamamoto Ryoichi 
Published: April 2011

AbstractThe electronic structure of AlS9 tilt grain boundary with segregated impurity atoms of Na, Ca, Si and S, respectively, has been investigated by an ab initio pseudopotential method. Na and Ca segregation causes the boundary to expand and the charge density to decrease significantly. There forms several weak bond regions. Si segregation increases the charge density between Si and the neighboring Al atom. There forms a stronger Al-Si bond that is a mixture of covalent and metallic character in the boundary. For S segregation, though there forms the stronger bond between Al and S atom, some Al-S bonds may become weaker than the former Al-Al bonds because of the charge density decrease. It is concluded that the mechanism of Na or Ca-promoted Al grain boundary embrittlement is one kind of ‘decohesion model’, that of Si is ‘bond mobility model’. It can't be decided the embrittlement mechanism by S segregation is classified into ‘bond mobility model’ or ‘decohesion model’.
Effect of Grain Boundaries and Indentation Load on the Electrical Properties of Nickel Base Super-alloys
Authors: Pinkos Kimberly , Laboy Celestina , Gerhardt Rosario A. 
Published: April 2011

AbstractWe have used impedance spectroscopy to evaluate the effect of the presence of grain boundaries and plastic deformation, as caused by hardness indentation, on the electrical response of several commercial nickel base super-alloys at room temperature. These alloys consist of a mostly nickel matrix that contains small precipitates of intermetallic phases such as Ni3Al or Ni3Ti(often referred to as gamma prime) as a reinforcing phase. Measurements were made as point contacts so that data could be tracked from point to point. Results indicate that the grain boundaries tend to have higher conductivities than the individual grains in most cases. It is speculated that this is due to the boundary regions having a different compositional profile than the center of the grains(as determined by gamma prime size, shape and distribution). Hardness indentation, on the other hand, had a more dramatic effect, by causing the magnitude of the imaginary impedance to change in size as well as position. Complementary microscopy results are included as supporting evidence for the effects discussed.