Computational Analysis of Core/Shell-like Structure Formation through Equilibrium Segregation in Ternary Compound Semiconductor Nanocrystals

ORAL

Abstract

We present a computational analysis of equilibrium surface segregation in nanocrystals of In$_{x}$Ga$_{1-x}$As, ZnSe$_{1-x}$Te$_{x}$, and ZnSe$_{1-x}$S$_{x}$. The analysis is based on coupled compositional, structural, and strain relaxation employing Monte Carlo and conjugate-gradient methods according to proper parameterizations within the valence-force-field (VFF) description. The VFF parameterizations are validated by comparisons of their segregation energy predictions with first-principles density functional theory (DFT) calculations. We report results for the equilibrium concentration distributions in the nanocrystals as a function of the compositional parameter x and nanocrystal size; the nanocrystal morphologies are polyhedral with distinct facets of low-index surface orientation as determined from DFT calculations of equilibrium crystal shapes. The results identify the particle-size and composition ranges that allow for assembly of core/shell-like nanocrystal structures with increased band-gap tunability.

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Authors

  • Sumeet C. Pandey

    Dept. of Chemical Engineering, Univeristy of Massachusetts, Amherst

  • Tejinder Singh

    Dept. of Chemical Engineering, Univeristy of Massachusetts, Amherst, University of Massachusetts Amherst, Department of Chemical Engineering, University of Massachusetts, Amherst

  • Triantafillos J. Mountziaris

    Dept. of Chemical Engineering, Univeristy of Massachusetts, Amherst, Department of Chemical Engineering, University of Massachusetts, Amherst

  • Dimitrios Maroudas

    University of Massachusetts, Amherst, Department of Chemical Engineering, University of Massachusetts, Amherst, MA 01003, Dept. of Chemical Engineering, Univeristy of Massachusetts, Amherst, University of Massachusetts Amherst, Department of Chemical Engineering, University of Massachusetts, Amherst