Size-controlled growth of germanium nanowires from ternary eutectic alloy catalysts

We report the size-controlled growth of Ge nanowires from Au-Ag-Ge ternary alloy catalysts. Significantly, Au-Ag-Ge layered thin films enabled, for the first time, the synthesis of high aspect ratio Ge nanowires by simultaneously manipulating both the solute concentration (C) and equilibrium concentration (C_eq.) of Ge in the catalysts, thereby increasing the Ge supersaturation during vapour-liquid-solid (VLS) growth. Simultaneous manipulation of C and C_eq. to enhance nanowire growth rates was also achieved using colloidal Au_0.75-Ag_0.25 nanoparticles deposited on a Ge film. These nanoparticles produced Ge nanowires with more uniform diameter distributions than those obtained from the thin films. The manifestation of the Gibbs-Thomson effect, resulting in a diameter dependent growth rate, was observed for all nanowires grown from Au_0.75-Ag _0.25 nanoparticles. In situ TEM heating experiments performed on the as-grown Ge nanowires enabled direct determination of the Ge equilibrium concentrations in the Au-Ag-Ge ternary alloys.