Morphological evolution of Ag nano-wires via thermal evaporation

Abstract

Recent progress in the synthesis and characterization of nano-materials has been driven by the need to understand the novel optical and electric properties of one-dimensional materials with a size in the range of a nanometer scale. Many research groups have focused their attention on the development of new nanomaterials that have potential applications in the fabrication technology of new types of electronic and photonic devices with nano-size. Various nano-wires including Si-based, metal oxides, metal sulfides, nitrides and metal/oxide composite nano-wires have been successfully synthesized by non-lithography methods including the vapor-phase transport process, laser ablation, arc discharge, solution and a template-based method [1–10]. A large part of such works has been focused on semiconductor systems including both element and compound semiconductors such as Si, Ge, GaN, GaAs and MgO, ZnO, and also oxide systems with insulation nature such as SiO2, GeO2, Ge2O3, Cu2O, SnO2 and PbO [10–20]. These nano-wires may have different morphologies and diameters. A few studies on metals exist in the literature. Metal nano-wires exhibit a number of interesting properties: their electrical conductance is quantized, their shot-noise is suppressed by the Pauli principle, and they are remarkably strong and stable. The metal nano-wires are expected to be used as components in new technology devices, as the size of the future electronic devices will be down to nano-scale. Intensive study focused on the fabrication of the metal and metal oxide nano-wires has been conducted recently, which has resulted in the synthesis of some metal nano-wires such as Ag, Ni, Cu and alloy nano-wires, including Fe-Co and Fe-Ni-Co based on electroplating, template and reduction process [21–23]. The Cu nano-wires have been synthesized via thermal evaporation [24, 25], but at present, the growth mechanism of metal nano-wires has not been completely elucidated. Therefore, synthesis of metal nano-wires is of importance from both the technological and scientific point of view. In this letter we report the fabrication of Ag nano-wires with the configurations of Ag cores covered by a thin amorphous SiOx shell at the outer surface via thermal co-evaporation of AgO and SiO powders in an inert gas mixed with hydrogen atmo-