Investigation of Ag-TiO₂ Interfacial Reaction of Highly Stable Ag Nanowire Transparent Conductive Film with Conformal TiO₂ Coating by Atomic Layer Deposition

The atomic layer deposition (ALD) technique is applied to coat Ag nanowires (NWs) with a highly uniform and conformal TiO₂ layer to improve the stability and sustainability of Ag NW transparent conductive films (TCFs) at high temperatures. The TiO₂ layer can be directly deposited on Ag NWs with a surface polyvinylpyrrolidone (PVP) coat that acts a bed for TiO₂ seeding in the ALD process. The ALD TiO₂ layer significantly enhances the thermal stability at least 100 fold when aged between 200–400 °C and also provides an extra function of violet-blue light filtration for Ag NW TCFs. Investigation into the interaction between TiO₂ and Ag reveals that the conformal TiO₂ shell could effectively prevent Ag from 1D-to-3D ripening. However, Ag could penetrate the conformal TiO₂ shell and form nanocrystals on the TiO₂ shell surface when it is aged at 400 °C. According to experimental data and thermodynamic evaluation, the Ag penetration leads to an interlayer composed of mixed Ag–Ag₂O-amorphous carbon phases and TiO_2–x at the Ag–TiO₂ interface, which is thought to be caused by extremely high vapor pressure of Ag at the Ag–TiO₂ interface at a higher temperature (e.g., 400 °C).