2014 TMS RF Mehl Medal Symposium on Frontiers in Nanostructured Materials and Their Applications: Nanomaterials for Device Applications and Nanometal III-Deformation Mechanisms
Sponsored by: TMS Electronic, Magnetic, and Photonic Materials Division, TMS: Thin Films and Interfaces Committee
Program Organizers: Nuggehalli Ravindra, New Jersey Institute of Technology; Ramki Kalyanaraman, University of Tennessee; Haiyan Wang, Texas A & M University; Yuntian Zhu, North Carolina State University; Justin Schwartz, North Carolina State University; Amit Goyal, Oak Ridge National Laboratories

Wednesday 2:00 PM
February 19, 2014
Room: Ballroom E
Location: San Diego Marriott Marquis & Marina

Session Chair: R. Katiyar, University of Puerto Rico; Somuri Prasad, Sandia National Lab

2:00 PM  Invited
Nanoengineered Binary and Ternary Heavy Metal Selenides for MWIR Detectors: Narsingh Singh1; 1University of Maryland, Baltimore County
    A large number of papers have been published in the past fifteen years on the growth and characterization of nanoparticles/nanowires of variety of materials. In spite of huge investment wide applications in systems applications has not been realized. There is a great potential for nanoparticles, nanodots and nanowires for their applications in electronic and optical devices and sensors since nanoparticles have shown that they can amplify the Raman scattering cross section of the molecules absorbed on them. Lead, mercury and thallium selenides have excellent properties for high operating temperature (HOT) mid infrared wavelength (MWIR) and long infrared wavelength (LWIR) detectors. We have performed experiments on the vapor growth of PbSe and HgSe and have demonstrated parameters for oriented nanocrystals on large substrates. We will describe the dependence of growth conditions on the morphology and relevant properties for novel devices and their progress.

2:20 PM  Invited
Electronically-active Silicon Nanophotonic Structures for Nonlinear Optics on a CMOS-compatible Chip: Shayan Mookherjea1; 1UC San Diego
    Traditionally, nonlinear optics conjures images of large vibration-isolated tables, powerful lasers, and painful alignment of optical components with many dozens of degrees of freedom. In contrast, chip-scale nonlinear optics, especially fabricated using CMOS tools in silicon, is stable, energy efficient, scalable and much more compact. This technology can enable practical applications of wavelength conversion, signal processing and quantum science. Here, we will review recent progress made in achieving record performance in classical and quantum optical four-wave mixing using nanostructured silicon photonic chip-scale devices with a few milliwatts of pump power.

2:40 PM  Invited
Fabrication, Characterization, and Mechanism of Vertically Aligned Titanium Nitride Nanowires: Seyram Gbordzoe1; Mainul Faruque1; Kwadwo M-Darkwa1; Zhigang Xu; Dhananjay Kumar2; 1North Carolina Agricultural and Technical State University; 2North Carolina A & T State University
    Titanium nitride (TiN) nanowires have been grown on single crystal magnesium oxide (MgO) substrates using a bottom-up pulsed laser deposition method where Ti-N based gaseous reactants in the laser plume supersaturate the catalytic gold (Au) liquid located on the substrate surfaces. Growth of TiN continues as long as the dissolution rate of material into the catalyst matches the extrusion of solid material at the liquid/solid interface. This bottom-up approach gives rise to a one-dimensional TiN nanowire structure (length: 200-300 nm and diameter: 20-30 nm) capped with a catalytic Au seed. The ascent of Au nanodots to the top of TiN nanowires can be explained based on breaking of weaker bonds and formation of stronger bonds. From strength point of view, these bonds are listed here in order of decreasing strength as follows: Ti-O (672 KJ/mol) > Ti-N (496 KJ/mol) > Au-N (416 kJ/mol) > Au-O (221 kJ/mol). The TiN nanowires were provided vertical alignment by selecting a plane of the substrate that provides the least lattice mismatching to the (111) plane of TiN which has lower surface energy than its other planes: (100) or (110).

3:00 PM  Invited
Novel Bimetallic Plasmonic Nanomaterials: Ritesh Sachan1; R. Kalyanaraman2; G. Duscher2; 1Oak Ridge National Laboratory; 2University of Tennessee
    We study Ag-Co bimetallic nanoparticles (NPs) due to its unique plasmonic characteristics. A self-organization route based on pulsed laser induced dewetting of bilayer metallic films is used to synthesize Ag-Co bimetallic plasmonic NPs. The far-field optical results showed that surface plasmon (SP) in Ag-Co NPs can be tuned over a wavelength range one order magnitude greater than that for pure Ag NPs. Ag-Co NPs show a life-time of nearly an order of magnitude higher than pure Ag NPs due to cathodic protection of Ag by galvanic coupling of Ag and Co within the NPs and thus show ultrastable optical properties. With near-field optical analysis by low-loss EELS, first known discovery of strong visible wavelength SP in Co region of bimetallic NPs was made which is unique finding due to well-known highly damped plasmonic nature of pure Co. This discovery is useful for making next generation bio-sensing devices.

3:20 PM  
Hollow Fiber Solar Cells: Processing, Morphology, and Property Correlations: Tyler Smith1; Abhinav Malasi1; Hernando Garcia2; Gerd Duscher1; Ramki Kalyanaraman1; 1University of Tennessee, Knoxville; 2Southern Illinois University Edwardsville
    In the field of photovoltaics, device architecture can play a lead role in increasing the efficiency of solar cells. One promising design is to make inorganic solar cells inside hollow polymer fibers. This geometry allows greater light absorption and increases the ratio of trapping length to recombination length, potentially leading to higher efficiency. This geometry can also result in low cost, lightweight, flexible and efficient solar cells for various applications, including as textiles and large area solar harvesters. In this study, we present results of CdS based Schottky device fabricated using low temperature chemical bath deposition (CBD) technique in planar and hollow fiber configurations. The electrical, optical and I-V characteristics of the Schottky device in correlation to processing and morphology characteristics will be presented. The eventual goal will be to fabricate inorganic heterojunction solar cells inside hollow fibers, enabling a new generation of low cost and high efficiency solar cells.

3:40 PM Break

4:00 PM  Invited
The Hall-petch Based Dislocation Mechanics of Nanopolycrystal Plasticity: Ronald Armstrong1; 1University of Maryland
    The dislocation mechanics aspects of the Hall-Petch based inverse square root of grain size dependence of strength and strain rate sensitivity are described for the range of conventional to nanopolycrystalline metals. Emphasis is placed on connection with the researches of Jay Narayan who has contributed both to the production of nano-materials and to assessment of their properties. Of particular interest here is evaluation of the H-P stress intensity (slope value), k, that is attributed to the requirement of activating secondary prism or pyramidal slip systems in the grain boundary regions of hexagonal close-packed (hcp) metals and of activating cross-slip at the grain boundary regions of face-centered cubic (fcc) metals; thus supplying an explanation of a lowest k value for aluminum at ambient temperature. A lowered value of k for nano-iron and steel materials is attributed to reduction of Cottrell-locking at grain boundary regions and to possible grain boundary disorder.

4:20 PM  Invited
Modeling of Grain Boundaries in Nanostructured Alloys: Structure, Stability and Dynamics: Shijing Lu1; Donald Brenner1; 1North Carolina State University
    Addition of solute atoms to nanostructured metals can have a profound influence on stability and mechanical properties. This can result from thermodynamic stabilization from solute segregation, or reduction of grain boundary mobility due to solute drag. We have been using a combination of density functional theory, molecular dynamics simulations and meso-scale defect modeling to better understand how the combined properties of solvent and solute atoms influence grain boundary stability and mobility. Three aspects of this work will be discussed, a perturbation approach that allows rapid calculation of solute substitution energies, simulations of the effect of grain boundary segregate density on grain boundary motion at high driving forces, and simulations combining Monte Carlo and molecular dynamics simulations to model grain boundary mobility at lower driving forces. This work was supported by a grant from the Office of Naval Research.

4:40 PM  Invited
The Role of Interfaces on the Deformation Behavior of Nanocrystalline Thin Films and Bulk Materials: Mathias Göken1; 1Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
    Nanocrystalline materials and thin films show a great potential concerning their mechanical properties. Although there mechanical properties have been investigated quite intensively, the role of interfaces on the deformation behavior is still discussed controversially. Investigations of thin Au-films and nanotwinned thin Cu-films with a bulge test inside an atomic force microscope show easy sliding and rotation of columnar grains in the thin films. This interface sliding probably also causes the found extremely low fracture toughness of the thin gold films. These results are in good agreement with nanoindentation experiments on bulk nanocrystalline materials where Focused Ion Beam cross sections clearly reveal sliding of grains out of the free surface. However, underneath the indenter inside the bulk, no direct evidence of interface sliding has been found. Here the constraints imposed from the neighboring grains, limit sliding of interfaces and require dislocation processes to be active during deformation.

5:00 PM  Invited
Friction Behavior of Nanocrystalline Metals: The Role of Subsurface Grain Structures: Somuri Prasad1; Corbett Battaile1; Henry Padilla1; Brad Boyce1; Paul Kotula1; 1Sandia National Laboratories
    Tribological behavior nancrystalline alloys (Ni, Ni-Fe, Au) was evaluated under a range of contact stresses and sliding speeds. Friction-induced microstructural changes in the subsurface regions were examined by TEM. At low sliding speeds (or normal forces), the steady-state COF decreased to µ≈0.2 whereas at higher sliding speeds and normal forces, the steady-state COF remained high, µ≈0.8. In cases that exhibited low friction behavior, subsurfaces revealed the presence of ultrafine nanocrystalline zones with 2-10 nm size grains, formed due to friction-induced deformation. We believe that the existence of these ultrafine nanocrystalline layers changed the deformation mechanism from the traditional dislocation mediated one to that predominantly controlled by grain boundaries. The key distinction between the high-friction and low-friction conditions appears to lie in the triggering of a delamination process. Finite element analysis is used to aid in the understanding of how the magnitude and location of stresses drive these two distinct regimes.

5:20 PM  Invited
3D TEM Characterization of Nanocrystalline Metal Thin Films: Xiaoxu Huang1; S. Schmidt1; P. Larsen1; H. H. Liu2; A. Godfrey3; Z. Q. Liu4; 1Technical University of Denmark; 2California Institute of Technology; 3Tsinghua University; 4Institute of Metal Research
    Characterization of nanocrystalline metal films using transmission electron microscopy (TEM) encounters difficulties to resolve multiple through thickness grains and to provide statistical data of grain orientations and grain boundary characteristics. We have employed a newly developed technique for three-dimensional orientation mapping in the TEM (3D-OMiTEM), which has a spatial resolution of 1 nm, to obtain 3D grain maps of nanocrystalline metal films produced by deposition processes. From the 3D grain maps, structural parameters such as size, shape and crystallographic orientation of individual grains, and normal, curvature and misorientation of grain boundaries in the volume analyzed, can be obtained. In this presentation, examples of 3D grain orientation maps generated from the 3D-OMiTEM are illustrated, showing the importance of using 3D techniques for a precise characterization of structural parameters of nanocrystalline metal films.