Abstract
In this work, the evolution of PdAg and PdAuAg alloy nanostructures is demonstrated on sapphire (0001) via the solid-state dewetting of multi-metallic thin films. Various surface configurations, size, and arrangements of bi- and tri-metallic alloy nanostructures are fabricated as a function of annealing temperature, annealing duration, film thickness, and deposition arrangements such as bi-layers (Pd/Ag), tri-layers (Pd/Au/Ag), and multi-layers (Pd/Au/Ag × 5). Specifically, the tri-layers film shows the gradual evolution of over-grown NPs, voids, wiggly nanostructures, and isolated PdAuAg alloy nanoparticles (NPs) along with the increased annealing temperature. In contrast, the multi-layers film with same thickness show the enhanced dewetting rate, which results in the formation of voids at relatively lower temperature, wider spacing, and structural regularity of alloy NPs at higher temperature. The dewetting enhancement is attributed to the increased number of interfaces and reduced individual layer thickness, which aid the inter-diffusion process at the initial stage. In addition, the time evolution of the Pd150 nm/Ag80 nm bi-layer films at constant temperature show the wiggly-connected and isolated PdAg alloy NPs. The overall evolution of alloy NPs is discussed based on the solid-state dewetting mechanism in conjunction with the diffusion, inter-diffusion, alloying, sublimation, Rayleigh instability, and surface energy minimization. Depending upon their surface morphologies, the bi- and tri-metallic alloy nanostructures exhibit the dynamic reflectance spectra, which show the formation of dipolar (above 700 nm) and quadrupolar resonance peaks (~ 380 nm) and wide dips in the visible region as correlated to the localized surface plasmon resonance (LSPR) effect. An absorption dip is readily shifted from ~ 510 to ~ 475 nm along with the decreased average size of alloy nanostructures.
Highlights
The recent growing interest in the development of nanodevice and applications is mainly focused on the technique to produce and design the multi-metallic nanostructures, semiconducting polymer as well as thermal transport of metal/semiconductor nanomembrane [1–10]
The fabrication of bi- and tri-metallic alloy nanostructures of Pd, Ag, and Au has been successfully demonstrated on sapphire (0001) via the solid-state dewetting
The various surface morphology of the alloy nanostructures were obtained by controlling the annealing temperature, time, and deposition scheme such as bi, tri, and multi-layers arrangement
Summary
The recent growing interest in the development of nanodevice and applications is mainly focused on the technique to produce and design the multi-metallic nanostructures, semiconducting polymer as well as thermal transport of metal/semiconductor nanomembrane [1–10]. Fabrication of PdAuAg and PdAg Alloy Nanostructures After the depositions, both the tri-layer and multi-layer samples showed smoother morphologies as shown in Additional file 1: Figure S1(c)–(d).
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