In situ Studies Revealing the Effect of Au Surfactant on the Formation of Ultra-Thin Ag Layers Using High-power Impulse Magnetron Sputter Deposition

Introducing metallic nanoparticles, such as Au, on the substrate as a surfactant or wetting inducer has been demonstrated as a simple but effective way to facilitate the formation of ultra-thin silver layers (UTSLs) during the following Ag deposition. However, most research paid much attention to the applications of UTSLs assisted by metallic surfactants but neglected the underlying mechanisms of how the metallic surfactant affects the formation of UTSL. Here, we apply in situ grazing-incidence wide-/small-angle X-ray scattering to reveal the effects of the Au surfactant or seed layer (pre-deposited Au nanoparticles) on the formation of UTSL by high-power impulse magnetron sputter deposition (HiPIMS) on a zinc oxide (ZnO) thin film. According to the comprehensive and in-depth analysis of the in situ X-ray scattering data, we observe that the pre-deposited Au nanoparticles can act as additional defects or growth cores for the sputtered Ag atoms despite using HiPIMS, which itself already forms many nucleation sites. As a result, the formation of a continuous and smooth UTSL is reached earlier in HiPIMS as compared with bare ZnO thin films. Based on the mechanism revealed by the in situ measurements, we provide insight into the formation of UTSL and further UTSL-based applications.