Epitaxial deposition of silver ultra-fine nano-clusters on defect-free surfaces of HOPG-derived few-layer graphene in a UHV multi-chamber by in situ STM, ex situ XPS, and ab initio calculations

The growth of three-dimensional ultra-fine spherical nano-particles of silver on few layers of graphene derived from highly oriented pyrolytic graphite in ultra-high vacuum were characterized using in situ scanning tunneling microscopy (STM) in conjunction with X-ray photoelectron spectroscopy. The energetics of the Ag clusters was determined by DFT simulations. The Ag clusters appeared spherical with size distribution averaging approximately 2 nm in diameter. STM revealed the preferred site for the position of the Ag atom in the C-benzene ring of graphene. Of the three sites, the C-C bridge, the C-hexagon hollow, and the direct top of the C atom, Ag prefers to stay on top of the C atom, contrary to expectation of the hexagon-close packing. Ab initio calculations confirm the lowest potential energy between Ag and the graphene structure to be at the exact site determined from STM imaging

Electrodeposited Cu2ZnSnS4 thin films

Cu2ZnSnS4 (CZTS) thin films have been prepared using Electrochemical Atomic Layer Deposition (EC-ALD and also by one-step conventional constant potential electrodeposition. Optimal deposition conditions were investigated using cyclic voltammetry (CV). Then, based on CVs results, CZTS films were grown employing EC-ALD deposition cycles using the sequence Au/S/Cu/S/Zn/S/Sn/S to form the desired quaternary compound. In parallel, conventional one-step electrodeposition was carried out at -0.85 V vs. Ag/AgCl over 1 hour. A thermal treatment in sulfur vapor was also investigated in an attempt to optimize the stoichiometry. The crystal structure of the films was characterized by XRD and micro Raman spectroscopy, while the morphology, thickness, topography and elemental composition were investigated using FIB-SEM and EDS.Fil: Valdes, Matias Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Modibedi, M.. Energy Materials; SudáfricaFil: Mathe, M.. Energy Materials; SudáfricaFil: Hillie, T.. National Centre For Nano-structured Materials; SudáfricaFil: Vazquez, Marcela Vivian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin