Abstract
In this paper, the modified solid-state dewetting (MSSD) of well-defined and various uniform Pt nanostructures is demonstrated by the auxiliary diffusion enhancement. The MSSD utilizes the introduction of metallic indium (In) layers with high diffusivity in between sapphire and platinum (Pt) layer, through which the global diffusion and dewetting of metallic atoms can be significantly enhanced. Subsequently, the In atoms can be sublimated from the NP matrix, resulting in the formation of pure Pt NPs. By the systematic control of In and Pt bi-layer thickness, various areal density, size and configuration of Pt NPs are demonstrated. The In2 nm/Pt2 nm bilayers establish very small and highly dense NPs throughout the temperature range due to the early maturation of growth. Intermediate size of NPs is demonstrated with the In45 nm/Pt15 nm bilayers with the much improved interparticle spacings by annealing between 650 and 900 °C for 450 s. Finally, the In30 nm/Pt30 nm bilayers demonstrate the widely connected network-like nanostructures. In addition, the finite difference time domain (FDTD) simulation is employed to exploit the local electric field distributions at resonance wavelengths. The dewetting characteristics of In/Pt bilayers is systematically controlled by the modifications of layer thickness and annealing temperature and is systematically described based on the diffusion of atoms, Rayleigh instability and surface energy minimization mechanism. The optical properties demonstrate dynamic and widely tunable localized surface plasmon resonance (LSPR) responses depending upon the various surface morphologies of Pt nanostructures.
Highlights
Metallic nanoparticles (NPs) have demonstrated valuable tunable plasmonic, optical, electrical and catalytic properties [1,2] and are essential components in various applications such as sensors [3], solar cells [4,5], bio-medicals [6] and catalysts [7]
The solid state dewetting (SSD) is a self-assembly approach of transforming metastable thin films into arrays of nanostructures via the thermal annealing below the melting point of elements utilized as shown in Figure 1(a,a-1) [33,34]
The sacrificial In layer showed great improvement for the tuning configuration and uniformity of low diffusivity metallic elements such as Pt and the capability of wide-range tunability was demonstrated for various size Pt NPs
Summary
Metallic nanoparticles (NPs) have demonstrated valuable tunable plasmonic, optical, electrical and catalytic properties [1,2] and are essential components in various applications such as sensors [3], solar cells [4,5], bio-medicals [6] and catalysts [7]. The incorporation of metallic NPs can significantly improve the light conversion efficiency of solar cells due to the enhanced light absorption in the visible range of solar radiation by the localized surface plasmon resonance (LSPR) [8]. Among various metallic NPs, the Pt NPs are generally catalytically active systems for various chemical reactions due to the enhanced catalytic properties [16,17]. The Pt catalysts have demonstrated high reactivity, inertness, stability on substrate and high hydrogen adsorption-desorption capability, which makes it unique material in the redox reactions, hydrogenation-dehydrogenation of compounds and electrocatalytic reactions for hydrogen evolution [18,19,20]
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