2014 TMS RF Mehl Medal Symposium on Frontiers in Nanostructured Materials and Their Applications: Nanoceramics I--Nanostructured Ceramics-oxides and Thin Film Interfaces
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

Tuesday 8:30 AM
February 18, 2014
Room: Ballroom E
Location: San Diego Marriott Marquis & Marina

Session Chair: Justin Schwartz, North Carolina State University; Haiyan Wang, Texas A&M University

8:30 AM  Invited
Resistive Switching Characteristics of Mixed Oxides: Ram Katiyar1; Rajesh Katiyar1; Shojan Pavunny1; Geetika Khurana1; Pankaj Misra1; 1University of Puerto Rico
    We have studied resistive switching phenomenon in mixed oxides, namely ternary oxides LaGdO3 and LaLuO3, multi-ferroic BiFeO3 and Graphene Oxide thin films. Except for the last one, we observed unipolar resistive switching with well defined switching voltages with initial forming process. Forming free bipolar switching was observed in case of Graphene Oxide. The switching mechanism in unipolar cases was found to follow formation of metallic filaments through the agglomeration of oxygen vacancies and metal atoms in films and their subsequent rupture on application of suitable bias voltages. While in case of Graphene Oxide it is believed to be due to the movement of oxygen ions from the bottom ITO electrode into the film and vice versa. The ratio of high and low resistance states was found to be much higher in case of unipolar switching compared to the case of bipolar switching. Details of these results will be presented.

8:50 AM  Invited
Growth of Multiferroic Thin-film Heterostructures: John Prater1; Srinivasa Rao2; Sudhakar Nori2; Jagdish Narayan2; 1U.S. Army Research Office; 2North Carolina State University
    Different approaches to strain engineering will be discussed in the context of the epitaxial growth of multiferroic thin-film heterostructures. The challenge is especially great for the case of growing these systems epitaxially on Si (100) substrates where large lattice-constant and thermal-expansion mismatches can lead to large residual strains. We report on the heteroepitaxial growth by pulsed laser deposition of various combinations of the multiferroic BiFeO3, and ferromagnetic La0.7Sr0.3MnO3 and Ni82Fe18 (permalloy, Py) thin films, which have been integrated on Si (100) substrates using epitaxial buffer layers of SrTiO3 and MgO/TiN. Approaches to controlling the strains arising from lattice mismatch, thermal mismatch and defect generation will be discussed. Structural and magnetic properties of these layered heterostructures will be presented.

9:10 AM  Invited
Oxides for Spintronics: Ashutosh Tiwari1; 1University of Utah
    Spintronics represents a new paradigm of electronics that utilizes both the electron’s charge as well as its spin. It has the potential to facilitate a new generation of logic and photonic devices having high-speed, large memory and ultra-low power consumption. The critical step in the functioning of a spintronic device is the injection and detection of spin-polarized carriers at the ferromagnet-semiconductor interface. Despite considerable efforts, efficient injection of spins into nonmagnetic semiconductors continues to be a major hurdle in this field. All the possible routs of injecting spin in semiconductors rely on oxides. In this talk, I will present some of our very exciting research going on in this field in my group at the University of Utah. Particular focus will be on the injection of spin-polarized carriers in semiconductors using electrical and thermal routes. Acknowledgements:Financial support from NSF through CEMRI Grant#1121252 and CAREER Grant#0746486 is thankfully acknowledged.

9:30 AM  Invited
Oxide Based Thin Films, Properties and the Role of Defect Mediation: Sudhakar Nori1; Jagdish Narayan1; 1North Carolina State University
    Although oxides and oxide based thin film systems are widely studied topics in general, yet they continue to surprise periodically by exhibiting interesting physical properties requiring newer insights in order to understand these properties in detail. This talk focuses on the interesting physical properties exhibited by oxide based thin film systems, namely, zinc oxide, vanadium oxide and other rare-earth based manganite heterostructures and the source of origin to some of these striking features such as room temperature ferromagnetism. Point defects like oxygen and zinc vacancies and interstitials are created during the non-equilibrium growth process of the ZnO films. Defect mediation occurs via the formation of oxygen vacancy-zinc interstitial defect complex (VO-IZn) that acts as a source of n-type conductivity while the oxygen and zinc vacancies result in the observed ferromagnetism by forming bound magnetic polarons.

9:50 AM  
Tunable Magnetotransport and Device Application through Controlling Structural Boundaries in Self-assembled Vertically Aligned Nanocomposite Thin Films: Wenrui Zhang1; Aiping Chen1; Quanxi Jia2; Judith MacManus-Driscoll3; Haiyan Wang1; 1Texas A&M University; 2Los Alamos National Laboratory; 3University of Cambridge
    Vertically aligned nanocomposite (VAN) thin films have recently served as an intriguing platform for obtaining significant understanding of the fundamental physics and exploring novel functionalities for potential technological applications. In this work, the magnetotransport properties of (La0.7Sr0.3MnO3)1-x:(ZnO)x (LSMO:ZnO) VAN films have been systematically investigated through varying underlying substrates and film compositions. The tunability and enhancement of their low-field magnetoresistance (LFMR) have been attributed to controllable grain and phase boundaries, which would greatly affect the formation of electron transport channels. Moreover, the heteroepitaxial LSMO:ZnO VAN films with comparable LFMR properties have been successfully integrated on silicon substrates, which is a critical step enabling the application of VAN films in future spintronic devices. The above results demonstrate that VAN architectures with unique microstructure and interfacial couplings could provide powerful ways for manipulating functionalities in oxide thin films.

10:10 AM Break

10:30 AM  Invited
Misfit Accommodation in Oxide Heterostructures: Matthew Chisholm1; Honghui Zhou2; Stephen Pennycook1; Jagdish Narayan3; 1Oak Ridge National Laboratory; 2University of Illinois at Urbana-Champaign; 3North Carolina State University
    We have conducted a detailed structural and spectroscopic study of VO2/NiO/Al2O3 heterostructures using aberration-corrected scanning transmission electron microscopy. Domain matching epitaxy appears to explain the NiO/Al2O3 interface, where we found 12 planes of NiO matching with 13 planes of Al2O3. The VO2/NiO interface is seen to be more complicated with transition region that is structurally and electronically distinct from both the NiO and VO2 films. In this transition region, the crystal structure of the growing vanadium oxide film adopts that of the underlying NiO layer. We find the oxidation state of vanadium increases from ~ 3+ to ~ 4+ with thickness, accompanied by increasing lattice disorder. Reasons for the two different interface reactions will be discussed. This study reveals an important aspect of vanadium oxide growth, i.e., the adaptive growth of an interface mediated phase that assists the structure transition at the VO2/NiO interface.

10:50 AM  Invited
Synchrotron Scattering Studies of the Metal-insulator Phase Transition and Local Domain Formation in VO2: John Budai1; Jonathan Tischler2; Alexander Tselev1; Andrei Kolmakov3; Olivier Delaire1; Michael Manley1; Eliot Specht1; Ayman Said2; Lynn Boatner1; Jagdish Narayan4; 1Oak Ridge National Laboratory; 2Argonne National Laboratory; 3Southern Illinois University; 4North Carolina State University
    Synchrotron x-ray facilities now provide a powerful suite of high-resolution tools for investigating local lattice structure and dynamics in nanostructured materials. We have combined several scattering techniques, including scanning microdiffraction, inelastic, and diffuse scattering to study phase evolution and domain formation inside VO2 microcrystals and epitaxial films. Vanadium dioxide has attracted considerable interest both for device applications and as an important model system for understanding coupled structural and electronic metal-insulator transitions. At ~67°C, the VO2 resistivity changes by ~4 orders of magnitude and the lattice changes from tetragonal to monoclinic (M1). In addition, applied strains are known to significantly impact the lattice structure, and monoclinic (M2) or triclinic VO2 phases can also be stabilized. Our scattering studies reveal how domain formation, interface orientations, strain distributions and lattice vibrations near the phase transition depend critically on external and internal stresses. Research supported by Materials Sciences and Engineering Division, U.S. DOE-BES.

11:10 AM  Invited
Routes to Low Defect Interfaces between rocksalt Oxides and Wurtzite Nitrides: Elizabeth Paisley1; Benjamin Gaddy1; James LeBeau1; Christopher Shelton1; Ramón Collazo1; Zlatko Sitar1; Douglas Irving1; Jon-Paul Maria1; 1North Carolina State University
    Low defect heteroepitaxial integration of oxide/nitride polar materials could enable novel functional electronics. In this talk we present results of density functional theory (DFT) integrated with experiment and characterization to investigate mechanisms important to the deposition of low defect (111) oriented rocksalt MgO, CaO, and MgxCa1-xO (MCO) onto (0001) oriented wurtzite GaN. Typically, high surface energy of the (111) polar orientation leads to faceting of the oxide and a highly defective thin film. This is overcome by use of a novel molecular beam epitaxy synthesis method that uses H2O as the source of oxygen. Structural characterization by STEM indicates that a finite number of defects persist. DFT results determine the growth window to enable low defect integration, rotational preferences of the MCO on GaN, atomistic mechanisms for persistence of defects in lattice matched MCO films, and electronic properties of the MCO/GaN interface. This work is supported through NSF grant DMR-1151568.

11:30 AM  
Simplex Network Modeling for Press-molded Ceramic Bodies Incorporated with Granite Waste: Leonardo Pedroti1; 1UENF
    Brazil is one of the largest producers and exporters of ornamental rocks in the world. Among them, stands the marble, granite itself, diorite, and gneiss, commercially known as granite and marble. The state of Espirito Santo is the main hub of the country stone installed in the region of Cachoeiro. Formed by a very fine powder, the waste generated by processing, is a major environmental problem. In this work were added different proportions of the sticky residue granite, comprising diamond wire on concrete for evaluation of mechanical properties, chemical and environmental assessed by the determination method simplex from a stroke cement using standard CP-V, the results demonstrate that the residues added to enhance some ratios the characteristics of the mixture, which help to reduce the environmental impact.