Evolution of Ternary AuAgPd Nanoparticles by the Control of Temperature, Thickness, and Tri-Layer

Sundar Kunwar,Jihoon Lee,Sushil Bastola,Mao Sui,Puran Pandey

doi:10.3390/met7110472

Sundar Kunwar, Jihoon Lee + Show 3 more

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https://doi.org/10.3390/met7110472

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Abstract

Metallic alloy nanoparticles (NPs) possess great potential to enhance the optical, electronic, chemical, and magnetic properties for various applications by the control of morphology and elemental composition. This work presents the fabrication of ternary AuAgPd alloy nanostructures on sapphire (0001) via the solid-state dewetting of sputter-deposited tri-metallic layers. Based on the systematic control of temperature, thickness, and deposition order of tri-layers, the composite AuAgPd alloy nanoparticles (NPs) with various shape, size, and density are demonstrated. The metallic tri-layers exhibit various stages of dewetting based on the increasing growth temperatures between 400 and 900 °C at 15 nm tri-layer film thickness. Specifically, the nucleation of tiny voids and hillocks, void coalescence, the growth and isolated nanoparticle formation, and the shape transformation with Ag sublimation are observed. With the reduced film thickness (6 nm), tiny alloy NPs with improved structural uniformity and spatial arrangement are obtained due to enhanced dewetting. The growth trend of alloy NPs is drastically altered by changing the deposition order of metallic tri-layers. The overall evolution is governed by the surface diffusion and inter-mixing of metallic atoms, Rayleigh-like instability, surface and interface energy minimization, and equilibrium state of the system. The UV-VIS-NIR reflectance spectra reveal the formation of an absorption band and reflectance maxima at specific wavelengths based on the morphology and composition of AuAgPd alloy NPs. In addition, Raman spectra analysis shows the modulation of intensity and peak position of natural vibration modes of sapphire (0001).

Highlights

Multi-metallic alloy NPs have garnered considerable research interest because of their wide range of structural and elemental tunability and functional diversity, making them applicable in many nanodevices and -technologies [1,2,3,4,5,6]
The alloy NPs were fabricated at various temperatures between 400 and 900 ◦ C for 450 s
The growth of alloy NPs can be divided into two steps: (i) void and nanocluster evolution, and (ii) nanoparticle evolution

Summary

Introduction

Multi-metallic alloy NPs have garnered considerable research interest because of their wide range of structural and elemental tunability and functional diversity, making them applicable in many nanodevices and -technologies [1,2,3,4,5,6]. The electronic heterogeneity, site-specific response, and combinational effect of constituent metals are some interesting features of the alloy NPs, which could not be achieved with monometallic NPs. At the same time, the alloy NPs can provide additional flexibility for tuning optical [7,8], catalytic [9,10,11,12,13], electronic, and magnetic [14,15,16] properties by controlling shape, size, and density [17] as well as elemental composition. The localized surface plasmon resonance (LSPR) frequency of alloy NPs can be modulated through the composition variation, which potentially enables many applications in the plasmonic, energy, and biomedical fields. The durability of Pd-based nanocatalysts has been significantly improved by the addition of Au in the NPs [18] and the incorporation of Pd into Ag NPs can demonstrate a red shift of plasmon resonance peak from 440 to 732 nm along with the increased Pd composition [19].

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