ICMCTF2011 Session TSP: TP Poster Session

Thursday, May 5, 2011 5:00 PM in Room Town & Country
Thursday Afternoon

Time Period ThP Sessions | Topic TP Sessions | Time Periods | Topics | ICMCTF2011 Schedule

TSP-2 Fabrication and Characterization of Nanocomposite Films
Shiuh-Chuan Her, Ting-Yu Shiu, Shou-Jan Liu (Yuan Ze University, Taiwan)
Carbon nanotubes (CNT) with superior mechanical, electrical and thermal properties are excellent candidates for nano-reinforcing polymer-based composites. In this work, the multi-walled carbon nanotube (MWCNT) reinforced epoxy films were prepared on the backlite substrate by a hot-pressing process. To control the thickness of the film, a spacer of thickness 200um was employed. The analytical relationship among the moduli of the film, substrate and film/substrate system was derived basing on the beam theory, from which the elastic modulus of the film was determined by the three-point-bending test. Compared to neat resin films, an increase of 16% and 33% in elastic modulus were obtained when 1 wt% and 2 wt% of MWCNTs were added, respectively. Nanoindentation tests were employed to determine the hardness and Young’s modulus of the film in the nanometric scale. The measured hardness and Young’s modulus of the nanocomposite film were found to depend on the penetration depth. Experimental results show that the hardness and Young’s modulus of the film were decreasing with the increase of the indentation depth. In general, the modulus measured by the bending test represents the global and practical properties of the film, while the modulus measured by the nanoindentation test indicates the local and inherent properties. Experimental results revealed that the localized Young’s modulus obtained by the nanoindentation test is higher than the global Young’s modulus obtained by the three-point-bending test. The addition of the MWCNTs into epoxy matrix exhibits significantly improvement in the Young’s modulus of the nanocomposite film compared with pure epoxy.
TSP-3 Alumina Template Assistance in Pt/Sn Core-Shell Nano-Sphere Fabrication
Chi-Liang Chen, Chien-Chon Chen, Yi-Sheng Lai (National United University, Taiwan)
In this work, platinum/tin (Pt/Sn) core-shell structures were deposited on anodizing aluminum oxide (AAO) substrate by sputtering technique. The Pt/Sn/AAO structures were characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The AAO template with highly ordered nano-arrays served as nucleation sites on the sidewall. It was found that Sn atoms were clustered as island on AAO sidewalls, following the Stranski–Krastanov nucleation and growth model, due to its high surface energy. The island-shaped morphology of clustered Sn atoms adjacent to the AAO sidewall provided a rough surface for subsequent deposition of Pt catalysts. The activity area of Pt was measured by cyclic voltammetry. The dependence of chemical activity of catalysts on the Pt thickness and Sn/AAO morphology was explored.
TSP-10 Why Taking Creep Material Behavior Into Account is of Great Importance
Peggy Heuer-Schwarzer, Nick Bierwisch (Saxonian Institute of Surface Mechanics, Germany)

It is widely known, that many soft materials (e.g. polymers) show very significant time dependence with respect to their mechanical properties, especially with respect to Young’s modulus and Yield strength or Hardness.

In this work it will be shown how dramatic the influence of this dependency on the mechanical performance of real coating-substrate systems could be. In order to avoid failure due to flawed stability and life time prediction by ignoring this material behavior this dependence must be taken into account.

By doing so, not only experimental difficulties must be overcome but also new concepts for the correct analysis and interpretation of the measured data are necessary. Especially for nanoindentation and scratch analysis the well known classical concepts do not suffice. The authors will present the necessary extensions of such classical models and how they have to be applied.
TSP-11 Interfacial Structure and Electrical Properties of Epitaxial NiSi2/Si Contacts Formed by a Solid-Phase Reaction in Ni-P/Si(100) System
Hsun-Feng Hsu, Chia-Liang Wu, Ting Hsuan Chen, Hwang-Yuan Wu (National Chung Hsing University, Taiwan)
As metal-oxide-semiconductor field-effect transistor (MOSFET) devices are shrunk to the nanometer scale, flat shallow metal/Si electrical contacts must be formed in the source/drain region. This work demonstrates a method for the formation of epitaxial NiSi2 layers by a solid-phase reaction in Ni-P/Si(100) samples. The results show that the sheet resistance remained low when the samples were annealed at temperatures from 400 to 700°C for 30 s. Furthermore, annealing at 700°C, an epitaxial NiSi2 layer with an atomically flat NiSi2/Si interface was formed. The cross-sectional TEM images of epitaxial NiSi2/Si contacts formed by annealing at various periods show that both (100) and {111} interfaces were formed in the initial stage, and only the (100) interface remained at an annealing period ≥ 20s. This phenomenon results by reducing the interface energy. Additionally, a strong dependence of the Schottky barrier height on the interfacial structure was found. Schottky barrier height decreased as a mount of (100) interface increased.
TSP-12 GDOES for Accurate and Well Resolved Thin Film and Coating Analysis
Peter Schaaf, Marcus Wilke, Lothar Spieß, Gerd Teichert, Henry Romanus (TU Ilmenau, Institut für Werkstofftechnik, Germany)

In the last years, glow discharge optical emission spectrometry (GDOES) gained more and more importance in the analysis of functional coatings. GDOES thereby represents an interesting alternative to common depth profiling techniques like AES and SIMS, based on its unique combination of high erosion rates and erosion depths, sensitivity, analysis of nonconductive layers and easy quantification even for light elements such as C, N, O and H. Starting with the fundamentals of GDOES, a short overview on new developments in instrument design for accurate and well resolved thin film analyses is presented.

The article focuses on the analytical capabilities of glow discharge optical emission spectrometry in the analysis of metallic coatings and thin films. Results illustrating the high depth resolution, confirmation of stoichiometry, the detection of light elements in coatings as well as contaminations on the surface or in interfaces will be demonstrated by measurements of: a multilayer system Cr/Ti on silicon, interface contaminations on silicon during deposition of aluminum, Al2O3-nanoparticle containing conversion coatings on zinc for corrosion resistance, Ti3SiC2 MAX-phase coatings by pulsed laser deposition and hydrogen detection in a V/Fe multilayer system. The selected examples illustrate that GDOES can be successfully adopted as analytical tool in the development of new materials and coatings. A discussion of the results as well as of the limitations of GDOES are presented.
TSP-14 Characterization and Properties of Multilayered BN/SiO2 Thin Films for Tailoring Thermal and Mechanical Contact Interfaces
Jianjun Hu, John Bultman (Air Force Research Laboratory/UDRI); Jamie Gengler (Air Force Research Laboratory/Spectral Energies); Chris Muratore, Andrey Voevodin (Air Force Research Laboratory)
In order to develop thermal and mechanical contact interfaces, multilayered BN/SiO2 thin films were deposited on Inconel and silicon substrates using a magnetron sputtering (MS) assisted pulsed laser deposition (PLD) system. The SiO2 layers were grown by magnetron sputtering of a silicon target with reactive oxygen gas added in the chamber, and the BN layers were homogeneously grown by pulsed laser ablation of a BN target. The SiO2 and BN layers were deposited alternatively on the substrates, and each layer was grown at a thickness of approximately 100 nm that was monitored with a calibrated quartz oscillator. There are some fundamental scientific motivations promoting this study on the BN/SiO2 multilayer films, e.g., the BN materials possess high thermal conductivity, low friction coefficient, high thermal shock resistance, chemical inertness and good thermal stability at high temperatures. In particular, the alternative SiO2 layers between BN layers were introduced to increase the through-thickness thermal resistance by phonon scattering at BN/SiO2 interfaces, as well as thermal protection by highly dissipating heat along BN surfaces so as to reduce local hot spots with less thermal stress. The microstructure and chemistry of the films were studied using X-ray diffraction, micro Raman spectroscopy, a focused ion beam, and transmission electron microscope associated with EDS and EELS spectrometers (which provided the information on both surface and in-depth film properties). A high-temperature tribometer was used to measure the friction coefficient of the films. The thermal conductivity was characterized with a time-domain thermoreflectance (TDTR) technique . Further thermal and mechanical measurements are sought to evaluate the films. Here the multilayer architecture of thin films can provide an effective approach to tailor the thermal and mechanical contact interfaces with a highly anisotropic thermal conductivity .
TSP-15 Atom Probe Reconstruction Limitations in the Quantification of Interfacial Intermixing in Multilayered Thin Films
Justin Brons (University of Alabama); Andrew Herzing, Ian Anderson (NIST); Gregory Thompson (University of Alabama)

Intermixing between thin film layers can alter mechanical and thermal transport properties, phase stability and growth textures. Quantification of the degree of intermixing is crucial to elucidate the mechanisms of intermixing and their scaling effect on properties as listed previously. Atom probe tomography has received considerable attention for this characterization because of its ability to identify and provide reconstructions of atoms with near atomic spatial 3D resolution. In general, these atom probe reconstruction algorithms assume a constant evaporation field across the surface of the specimen. In reality, chemical inhomogeneity (i.e. discrete interfaces) modulates the evaporation field at the specimen surface. This introduces reconstruction artifacts and degrades the spatial resolution of the atom probe tomography technique. Multilayer thin films provide ideal specimen geometries to measure and quantify these artifacts. Thin films can be deposited with near atomic layer precision and can exhibit large planar surfaces with various degrees of intermixing across the interfaces. A series of Fe/Ni and Ti/Nb multilayers with bilayer repeat distances of 4 nm and 10 nm have been sputter-deposited onto n-doped Si [001] substrates. The multilayers were annular focus ion beam milled into the required needle-shaped geometry for the atom probe analysis with the film interfaces oriented with the bilayer chemical modulations parallel and perpendicular to the specimen apex. This was done to compare field evaporation behavior at these limiting geometries. The atom probe compositional profiles were then compared to Electron Energy Loss Spectroscopy (EELS) compositional profiles to determine the fidelity of the reconstructions through cross-comparison microscopy. The best agreement between the profiles was seen for Fe/Ni (similar field strengths) in a perpendicular-to-the-apex orientation.
TSP-16 Wear Properties of Thick TiSiCN Coatings
Jun-Feng Su, Ying Chen, Xueyuan Nie (University of Windsor, Canada); Ronghua Wei (Southwest Research Institute); Sean Cui (University of Windsor, Canada)

Hard coatings with large coating thicknesses have been increasingly considered as protective surface layers for improved wear resistance of key mechanical components. With plasma-enhanced magnetron sputtering (PEMS) technology, a series of thick carbonitride TiSiCN coatings were deposited on H13 steels. Using enhancement of ion bombardment prior to and during deposition to increase the coating adhesion and limit columnar growth, single-layered TiSiCN coatings with the coating thickness of 30-490 microns have been successfully prepared. Morphology and microstructure were analyzed using optical and scanning electron microscopes and X-ray diffraction. While nanoindentation was performed to determine the hardness and Young's modulus with mapping, pin-on-disk and impact-sliding tests were conducted to evaluate the wear resistance of the coatings. The relationship between thickness and wear properties were particularly discussed.
TSP-17 Pressure Cell for Thermal Conductivity Measurement of Thin Films under Applied Stress with the Time Domain Thermoreflectance Technique
John Bultman, Arthur Safriet (Air Force Research Laboratory/UDRI); Jamie Gengler (Air Force Research Laboratory/Spectral Energies); Adam Waite (Air Force Research Laboratory/UTC); Chris Muratore, John Jones (Air Force Research Laboratory); Brandon Howe, Ivan Petrov (University of Illinois at Urbana-Champaign)
Recently the time domain thermoreflectance (TDTR) technique has received much attention as a reliable method for measuring thermal conductivity of thin films. The technique relies on the change in surface reflectance measured with a laser probe beam under the temperature change induced with a laser pump beam. The technique is very versatile and was shown to be operated at different temperature regimes. Thermal conductivity of thin films can be also influenced by surface stress conditions, which for some of the film interfaces can be on the order of 1 GPa due to either mechanical or thermal expansion induced loads. It is then necessary to have a method of thin film thermal conductivity measurements under stressed conditions. This abstract discusses the design of a pressure cell, where thin films are subjected to a regulated pressure (up to 175 MPa), while allowing for the entrance and precise alignment of both pump and probe laser beams needed for the TDTR technique. The design incorporates a custom made piezo-element which can allow for either in-situ stress measurements or be used as an additional actuator of steady and oscillating stress fields. Femtosecond laser pump pulses are then applied to the stressed thin film surfaces and probe beam reflectivity data is fit with models for thermal diffusivity to extract the data on thin film thermal conductivity and interface thermal resistance. The cell was used for Al, SiO2, MoS2, composite, and polymer films to derive thermal conductivity at different thin film stress conditions.
TSP-20 Thermal Properties of Metal/Carbon Interfaces
Chris Muratore (Air Force Research Laboratory); Sergei Shenogin (UES/Air Force Research Laboratory); Jamie Gengler (Air Force Research Laboratory/Spectral Energies); Jianjun Hu (Air Force Research Laboratory/UDRI); Ajit Roy, Andrey Voevodin (Air Force Research Laboratory)
Most applications of carbon nanotubes require contact with more ordinary materials, such as metals or polymers. Unfortunately, the extraordinary thermo-electro-mechanical properties of nanotubes are often negated at the interface between the nanotubes and whatever they touch, resulting in a major shortfall between the measured and predicted performance of nanotube-based materials. One of the most troubling discrepancies in projected versus measured properties is found in thermal conductivity measurements of nanotube-containing composite materials. For example, a continuous network of thermally conductive nanotubes (or about 1 percent, by volume) within an organic matrix (k = 0.3 W m-1 K-1) should yield a 30-fold increase in thermal conductivity over the pure matrix phase alone, based on simple effective medium theory. Despite this potential increase, experimental results typically show an increase of only a factor of 2 at best in composites with nanotube additives. To better understand the nature of interfacial resistance in carbon nanotubes, modeling and experimental studies investigating engineered interfaces on highly oriented pyrolytic graphite (HOPG) samples were conducted. This substrate was selected as a practical 2-dimensioinal analog for nanotube sidewalls to facilitate modeling and experimentation. Molecular dynamics simulations of heat transfer through metal carbon interfaces were conducted, and measurements of thermal conductance at these interfaces were made by analysis of the time-domain thermoreflectance data from the samples. Metal films were selected to identify effects of atomic mass, chemical interactions with graphite and mechanical properties. For example, metals known to exhibit in situ formation of an interfacial carbide layer when in contact with a carbon source and heated, such as titanium and boron, were investigated, and the effect of this carbide layer formation on interfacial conductance was examined. Graded and sharp interfaces were also considered with computational and experimental efforts.
TSP-21 Pressure Dependence on Thermal Conductivity and Interface Conductance of Interface Materials for Thermal Switching
Adam Waite (Air Force Research Laboratory/UTC); Jamie Gengler (Air Force Research Laboratory/Spectral Energies); John Jones, Chris Muratore, Andrey Voevodin (Air Force Research Laboratory)
A cross-linked fluoropolymer/Ag nanocomposite for use as a thermal interface material in thermal switching applications was developed in a dual chamber Plasma Enhanced Chemical Vapor Deposition (PECVD) and magnetron sputtering system. The cross-linked fluoropolymer matrix material is an polymer thin film with low hardness (0.2 GPa), high Young’s modulus (5.3 GPa), and ultra low thermal conductivity (~0.08 W/m*K). Processing conditions to control the size and volume fraction of metallic nanoparticles, determined by electron microscopy, within the polymer matrix were identified. Thermal conductivity of composites containing different volume fractions of metallic nanoparticle inclusions were measured with the time domain thermal reflectance (TDTR) technique to identify the percolation threshold (approximately 25 volume percent) by an increase in thermal conductivity beyond that expected from effective medium theory. Composite materials of different compositions above and below the percolation threshold were investigated in a pressure cell that allowed application of over 10 MPa during TDTR experiments, and also allowed microscopic observation of the interface. The effects of pressure on thermal conductivity were examined to evaluate performance of the composite as a pressure-actuated thermal switch, and compared to other standard and novel thermal interface materials. Mechanical properties of composites before and after application of pressure were also investigated to determine potential for repeated use as a switch.
Time Period ThP Sessions | Topic TP Sessions | Time Periods | Topics | ICMCTF2011 Schedule