In situ studies revealing the effects 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 a 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 subsequent Ag deposition. However, most studies have 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. Herein, we have applied 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. The comprehensive and in-depth analysis of the in situ X-ray scattering data revealed that the pre-deposited Au nanoparticles can act as additional defects or growth cores for the sputtered Ag atoms despite using HiPIMS, which itself forms many nucleation sites. As a result, the formation of a continuous and smooth UTSL is reached earlier in HiPIMS 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.

High-Power Impulse Magnetron Sputter Deposition of Ag on Self-Assembled Au Nanoparticle Arrays at Low-Temperature Dewetting Conditions.

Plasmons have facilitated diverse analytical applications due to the boosting signal detectability by hot spots. In practical applications, it is crucial to fabricate straightforward, large-scale, and reproducible plasmonic substrates. Dewetting treatment, via applying direct thermal annealing of metal films, has been used as a straightforward method in the fabrication of such plasmonic nanostructures. However, tailoring the evolution of the dewetting process of metal films poses considerable experimental complexities, mainly due to nanoscale structure formation. Here, we use grazing-incidence small- and wide-angle X-ray scattering for the in situ investigation of the high-power impulse magnetron sputter deposition of Ag on self-assembled Au nanoparticle arrays at low-temperature dewetting conditions. This approach allows us to examine both the direct formation of binary Au/Ag nanostructure and the consequential impact of the dewetting process on the spatial arrangement of the bimetallic nanoparticles. It is observed that the dewetting at 100 °C is sufficient to favor the establishment of a homogenized structural configuration of bimetallic nanostructures, which is beneficial for localized surface plasmon resonances (LSPRs). The fabricated metal nanostructures show potential application for the surface-enhanced Raman scattering (SERS) detection of rhodamine 6G molecules. As SERS platform, bimetallic nanostructures formed with dewetting conditions turn out to be superior to those without dewetting conditions. The method in this work is envisioned as a facile strategy for the fabrication of plasmonic nanostructures.

Diblock copolymer pattern protection by silver cluster reinforcement.

Pattern fabrication by self-assembly of diblock copolymers is of significant interest due to the simplicity in fabricating complex structures. In particular, polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP) is a fascinating base material as it forms an ordered micellar structure on silicon surfaces. In this work, silver (Ag) is applied using direct current magnetron sputter deposition and high-power impulse magnetron sputter deposition on an ordered micellar PS-b-P4VP layer. The fabricated hybrid materials are structurally analyzed by field emission scanning electron microscopy, atomic force microscopy, and grazing incidence small angle X-ray scattering. When applying simple aqueous posttreatment, the pattern is stable and reinforced by Ag clusters, making micellar PS-b-P4VP ordered layers ideal candidates for lithography.