Oxidized copper seed layer for ultrathin and semi-transparent silver films

Abstract

In this study, we focused on the fabrication of highly transparent and lowly percolated ultrathin silver films on dielectric substrates, which find extensive applications in optoelectronic devices. Incorporating a seed layer is a popular technique for obtaining ultrathin continuous silver (Ag) films with reduced percolation thresholds. Here in this work, we explored the use of sub-nanometric thermally treated copper (Cu) thin film as a seed layer for growing highly transparent and conductive Ag films on silica substrates. Conventionally, the growth of Ag films on oxide substrates results in an island-like structure with large grain sizes and higher root mean square (RMS) surface roughness. However, our findings showed that by incorporating a thermally oxidized Cu seed layer, we could significantly reduce the RMS surface roughness to <1 nm and lower the percolation threshold up to 2 nm. To confirm the layer-by-layer growth of the Ag films, we employed X-ray diffraction analysis, which revealed a reduction in grain size and the formation of a continuous film when thermally oxidized Cu was used as a seed layer. We have also compared the results with Ag films seeded with unoxidized Cu. The incorporation of the thermally oxidized Cu seed layer resulted in Ag films with lower percolation thickness and higher IR transmittance, while the addition of the pristine Cu seed layer produced highly conductive and smoother Ag films.