When 10:30 AM - 11:30 AM Nov 20, 2015
Where 1571 G.G. Brown
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Non-Equilibrium Approaches to Understand the Growth and Assembly of Functional Nanostructures from Ultrasmall “Building Blocks”


David Geohegan
Oak Ridge National Laboratory, Center for Nanophase Materials Science

Understanding the link between the growth mechanisms of materials and their atomic structure is essential to design revolutionary new forms of matter with tailored properties – one of the grand challenges for the basic architecture of matter. Here we describe recent progress on in situ laser spectroscopy and imaging techniques to understand and control the growth of nanomaterials for functional applications – from ultrathin one- and few-layer 2D crystals of graphene and metal chalcogenides, to highly structured coatings of aligned nanotubes or mesoporous nanoparticle architectures. Laser-based techniques such as interferometry, absorbance, Raman scattering, and photoluminescence will be described that serve as remote optical probes to measure and control nanomaterial properties, and measure nucleation and growth kinetics for the development of growth models. One of the key goals in controllable nanomaterial synthesis is the identification of the key “building blocks” involved, and the kinetic pathways by which they are assembled. For this purpose, pulsed reactant delivery and time-resolved, in situ laser spectroscopy and imaging have been employed to understand and control the growth of single-wall carbon nanotubes, graphene, oxide nanostructures, and two-dimensional metal chalcogenide crystals. In addition to commonly-used chemical vapor deposition and vapor transport methods, pulsed laser deposition with its high kinetic energy and digital delivery of reactants is a remarkably versatile method to grow all of these materials. Recent work in the synthesis of ultrasmall amorphous nanoparticles by pulsed laser vaporization and their use as “building blocks” in the synthesis of both oxide and metal chalcogenide nanostructures will be described, and compared with traditional methods. These real-time diagnostic measurements are correlated with predictive theoretical methods and post-growth characterization by imaging, spectroscopy, and atomic-resolution analytical electron microscopy, to develop a framework for the deterministic synthesis of nanomaterials with desired properties. These capabilities and others available to users at the Center for Nanophase Materials Sciences (CNMS), one of five Dept. of Energy Nanoscale Science Research Centers, will be described.

 

Research sponsored by the U.S. Dept. of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Div. (synthesis science) and Scientific User Facilities Div. (characterization science).

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