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HL: Fachverband Halbleiterphysik
HL 34: Quantum dots and wires: Theory
HL 34.2: Talk
Tuesday, March 12, 2013, 09:45–10:00, H15
Modeling the interface between GaAs nanowire and Au capping: First principles study — •Sung Sakong, Yaojun A. Du, and Peter Kratzer — Fakultät für Physik and Center for Nanointegration (CENIDE), Universität Duisburg-Essen, Duisburg, Germany
We present first-principles calculations of the interface between a Au nanoparticle and a GaAs nanowire. The interfaces are modeled with Au ad-layers on a GaAs(111)B substrate. The GaAs surface can be terminated with As or Ga which reflects the two extreme cases in the growth process. The interface energies of As- and Ga-terminated interfaces are expressed as a function of As chemical potential µAs. Under Ga(As) rich growth, the Ga(As)-terminated interface becomes more stable than the other. We note that under a specific µAs the two interface energies become equal, i.e. the two terminations are energetically competing configurations and a layer-by-layer growth of the GaAs nanowire is possible. When one interface is dominantly more stable than the other, then a bilayer growth mode is preferred. The layer-by-layer growth of GaAs nanowire is at µAs−µAsbulk=−0.28 eV in LDA density functional. Using the estimated interface energy of 47 meV/Å2, we explore the optimal geometric structures of a Au capped GaAs nanowire with minimizing the surface free energy under near-equilibrium growth. With replacing the pure Au layers with a Au7Ga2 alloy, we are able to simulate an interface to a more Ga-rich nanoparticle. The interface energy of the Au-Ga alloy interface is smaller than the pure Au interface, which results in a more flat nanoparticle geometry due to the Gibbs-Thompson effect.