Direct Synthesis of Silicon Wires on a Polymer Substrate without the Substrate Heating using Hot-Wire-Enabled VLS Method

Rapidly growing field of flexible electronics calls for the coupling of modern nanomaterials and polymeric substrates. Silicon nanowires (SiNWs) grown by Vapor-Liquid-solid (VLS) mechanism are a preferred material for advanced electronic devices on account of their tunable properties and growth compatibility with any substrate. However, no report of direct growth of SiNWs on low operating temperature (~150°C) polymeric substrates is available as yet. In the present work, synthesis of Silicon wires (SiWs) having an average diameter in the sub-micrometre range has been successfully attempted directly on a polymer sheet (Kapton) via the reduction of an Indium Tin Oxide (ITO) film to In-Sn metal alloy particles followed by the synthesis of SiWs without the substrate heating by HotWire Chemical Vapor Processing technique. These SiWs were synthesized using a variation of the conventional VLS method wherein the hot wire plays a vital role for the growth of SiWs on low-melting-point ($\leq$156°C) In-Sn metal alloy particles. We therefore call this as the Hot-Wire-Enabled VLS (HW-VLS) method. The surface layer of In-Sn metal alloy particles formed after the reduction exhibit two distinct size distributions with average particle sizes and densities to be$\sim $58nm, 4x1$0^{9}{c}\mathrm{m}^{-2}$and$\sim $310nm, 2.2x1$0^{8}{c}\mathrm{m}^{-2}$. SiWs grown using these particles as a seed layer have a good density with an average diameter of $\sim $550 nm and a high growth rate of$\sim $7.4nm/sec. The direct growth as proposed in the present scheme has an added advantage of facile and cost-effective fabrication with fewer processing steps.