Semi-transparent, flexible, and electrically conductive silicon mesh by capillarity-driven welding of vapor-liquid-solid-grown nanowires over large areas

Bottom-up synthesis of semiconductor nanowires (NWs) by the vapor-liquid-solid (VLS) mechanism has enabled diverse technological applications for these nanomaterials. Unlike metallic NWs, however, it has been challenging to form large-area interconnected NW networks. Here, we generate centimeter-scale meshes of mechanically and electrically interconnected Si NWs by sequentially growing, collapsing, and joining the NWs using a capillarity-driven welding mechanism. We fabricate meshes from VLS-grown NWs ranging in diameter from 20 to 100 nm and find that the meshes are three-dimensional with a thickness ranging from ~ 1 to ~ 10 microns depending on the NW diameter. Optical extinction measurements reveal that the networks are semi-transparent with a color that depends on the absorption and scattering characteristics of individual NWs. Moreover, active voltage contrast imaging of both centimeter- and micron-scale meshes reveals widespread electrical connectivity. Using a sacrificial layer, we demonstrate that the mesh can be liberated from the growth substrate, yielding a highly flexible and transparent film. Electrical transport measurements both on the growth substrate and on liberated, flexible films reveal electrical conduction across a centimeter scale with a sheet resistance of ~ 160-180 kΩ/square that does not change significantly upon bending. Given the ability to encode complex functionality in semiconductor NWs through the VLS process, we believe these meshes of networked NWs could find application as neuromorphic memory, electrode scaffolds, and bioelectronic interfaces.