Substrate-engineered growth of ITO nanowires for advanced transparent electrodes with tunable sheet resistance and wettability

This study introduces a novel two-step approach for fabricating high-performance transparent conducting films. The method involves depositing a highly conductive flat indium tin oxide (ITO) base layer via magnetron sputtering under conventional conditions, followed by a top layer of ITO nanowires deposited by magnetron sputtering without oxygen in the process gas. We demonstrate that this architecture synergistically combines the low sheet resistance of the dense base layer with the antireflective properties of the nanowire layer, resulting in enhanced light transmittance. Crucially, the predeposited ITO layer significantly facilitates nanowire nucleation, enabling their growth at reduced temperatures compared to direct deposition on bare glass. Sputtering on bare glass and ITO-precoated substrates at temperatures ranging from 200 to 550 °C was used to elucidate substrate- and temperature-dependent growth mechanisms. Energy-dispersive x-ray mapping demonstrated substrate-dependent tin depletion in nanowire bodies and pronounced tin segregation at nanowire tips, governed by diffusion dynamics. Furthermore, the nanostructured surface imparts tunable wettability, transitioning from hydrophilic on bare glass to highly hydrophobic, with contact angles as high as 140°, on the ITO-coated substrates. This engineered substrate strategy provides a practical and scalable route to produce high-performance transparent electrodes with tailored functional properties for optoelectronics, surface applications, and microfluidic systems.