Speaker: Vivek B. Shenoy
Affiliation: University of Pennsylvania, USA
Abstract Details: Crystalline 2D materials such as graphene, boron nitride, transition metal dichalcogenides and composites of these materials have received attention for their potential applications in logic, energy storage and optoelectronics. Chemical Vapor deposition has become a common method for large-scale synthesis of these materials. This growth process is influenced by thermodynamic, kinetic, and material parameters, often leading to diverse island shapes including dendrites, squares, stars, hexagons, butterflies, and lobes. Here, we introduce a phase-field model that provides a unified description of these diverse growth morphologies of graphene and compare the model results with new experiments[1]. Our model explicitly accounts for the anisotropies in the energies of growing graphene edges, kinetics of attachment of carbon at the edges, and the crystallinity of the underlying copper substrate (through anisotropy in surface diffusion). We show that anisotropic diffusion has a very important, counterintuitive role in the determination of the shape of islands, and we present a “phase diagram” of growth shapes as a function of growth rate for different copper facets. Our results are shown to be in excellent agreement with growth shapes observed for high symmetry facets such as (111) and (001) as well as for high-index surfaces such as (221) and (310). I will also talk about our work on using defects in graphene and other 2D materails to enhance energy storage capacity [2]. [1] E. Meca, J. Lowengrub, H. K. Kim, C. Mattevi, and V. B. Shenoy Epitaxial Graphene Growth and Shape Dynamics on Copper: Phase-Field Modeling and Experiments NANO LETTERS 13(11) 5692-5697 (2013). [2] R. Mukherjee, A. Thomas, D. Datta, E. Singh, J. Li, O. Eksik, V. B. Shenoy, and N. Koratkar Defect Induced Plating of Lithium Metal within Porous Graphene Networks NATURE COMMUNICATIONS 5:3710 (2014). [3] D. Datta, J. Li and V. B. Shenoy Defective graphene as a high-capacity anode material for Na- and Ca-ion batteries ACS NANO, 6(3): 1788-1795 (2014).Click HERE for directions

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