Ultrathin Gold Nanowires for Transparent Electronics: Breaking Barriers

Novel types of Transparent Conductive Materials (TCMs) based on metal nanostructures are discussed. Dispersed metal nanoparticles can be deposited from liquids with moderate thermal budgets to form conductive films that are suitable for thin-film solar cells, displays, touch screens, and nanoelectronics. We aim at new TCMs that combine high electrical conductivity with optical transparency and mechanical flexibility. Wet-processed films of randomly arranged metallic nanowires networks are commercially established and provide a relatively cost-effective, scalable production. Ultrathin gold nanowires (AuNWs) with diameters below 2 nm and high aspect ratios have recently become available. They combine mechanical flexibility, high optical transparency, and chemical inertness. AuNWs carry oleylamine capping ligands from synthesis that cause high contact resistances at their junctions. We investigated different annealing processes based on temperature and plasma treatment, to remove the ligands after deposition and to allow electrical conductivity. Their effect on the resulting nanostructure and on the material properties was studied. Scanning Electron Microscopy (SEM) and optical spectroscopy revealed changes in the microstructure for the different post-treatments. We found that the conductivity and the stability of the TCM depended strongly on its final microstructure. We demonstrate that the best results are obtained using H2-plasma treatment.