Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 38: [DS] Progress in Micro- and Nanopatterning: Techniques and Applications II (Focused Session, jointly with O - Organisers: Graaf, Hartmann)
O 38.1: Vortrag
Mittwoch, 16. März 2011, 11:00–11:15, GER 38
Tuning the electrical conductivity of Pt-containing granular metals by postgrowth electron irradiation — •Fabrizio Porrati, Roland Sachser, Christian H. Schwalb, and Michael Huth — Physikalisches Institut, Goethe-Universität, D-60438 Frankfurt am Main, Germany
We have fabricated Pt-containing granular metals by focused electron beam induceddeposition from the (CH3)3CH3C5H4Pt precursor gas. The granular metals are made of platinum nanocrystallites embedded in a carbonaceous matrix. We have exposed the as-grown nanocomposites to low energy electron beam irradiation and we have measured the electrical conductivity as a function of the irradiation dose. Postgrowth electron beam irradiation transforms the matrix microstructure and thus the strength of the tunnel coupling between the Pt nanocrystallites. For as-grown samples (weak tunnel coupling regime) we find that the temperature dependence of the electrical conductivity follows the stretched exponential behavior characteristic of the correlated variable-range hopping transport regime. For briefly irradiated samples (strong tunnel coupling regime) the electrical conductivity is tuned across the metal-insulator transition. For long-time irradiated samples the electrical conductivity behaves like that of a metal. In order to further analyze changes of the microstructure as a function of the electron irradiation dose we have carried out atomic force microscopy (AFM) and micro-Raman measurements. These measurements reveal that by increasing the irradiation dose the matrix changes following a graphitization trajectory between amorphous carbon and nanocrystalline graphite.