Abstract
Alloy nanoparticles (NPs) can offer a wide range of opportunities for various applications due to their composition and structure dependent properties such as multifunctionality, electronic heterogeneity, site-specific response, and multiple plasmon resonance bands. In this work, the fabrication of self-assembled PdxAg1-x NPs alloy nanostructures with distinct size, density, shape, and composition is demonstrated via the solid-state dewetting of sputtered Pd/Ag thin films on c-plane sapphire. The initial stage of bilayer dewetting exhibits the nucleation of voids, followed by the expansion of voids and cluster breakdown and finally shape transformation along with the temperature control. Bilayer composition shows a substantial influence on the dewetting such that the overall dewetting is enhanced along with the increased Ag composition, i.e. Pd0.25Ag0.75 > Pd0.5Ag0.5 > Pd0.75Ag0.25. On the other hand, the size and density of NPs can be efficiently controlled by varying the initial thickness of bilayers. Reflectance peaks in UV and near-infrared (NIR) regions and a wide absorption band in the visible region arisen from the surface plasmon resonance are observed in reflectance spectra. The peak intensity depends on the composition of PdxAg1-x NPs and the NIR peaks gradually blue-shift with the size decrement.
Highlights
Metallic alloy NPs have gained increasing research attention due to the added possibility of tuning optical, electronic and catalytic properties by controlling the alloy composition and surface morphology [1,2,3]
Metal films deposited on substrates at ambient temperature are unstable or metastable, which normally dewet into isolated particles along with an appropriate annealing to gain thermodynamic stability with the lowest surface energy
The Pd–Ag alloy NPs were fabricated on sapphire (0 0 0 1) using sputtering deposition technique and subsequent annealing
Summary
Metallic alloy NPs have gained increasing research attention due to the added possibility of tuning optical, electronic and catalytic properties by controlling the alloy composition and surface morphology [1,2,3]. Interaction between NPs and supporting material, which can be appropriately modulated by the control of structure and composition of NPs. the fabrication of Pd–Ag alloy NPs by the solid stage dewetting on sapphire (0 0 0 1) and the systematic study on their structural and optical properties can be an important foundation for many potential applications, which is not yet reported up to date. The Raman spectra analysis is performed to probe the strain effect and crystal properties of sapphire after PdxAg1-x NPs fabrication
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