Plasmonic Pt Nanocrystals by Using a Sacrificial In Component via the Enhanced Dewetting on Sapphire (0001): Improvement on Morphological and Localized Surface Plasmon Resonance Properties

Modulation of functional metallic nanoparticles (NPs) in terms of their size, configuration, and dimension can offer a promising route to control the optical, catalytic, magnetic, and sensing properties for a wide range of applications. Herein, the platinum (Pt) nanostructures of improved morphological and localized surface plasmon resonance properties are demonstrated via the enhanced solid-state dewetting by using a sacrificial indium (In) layer on sapphire (0001). Upon annealing, the concurrent occurrence of intermixing between In and Pt atoms, formation of In-Pt alloy and sublimation of In atoms plays major roles in accelerating the dewetting process, which results in the formation of definite Pt nanostructures. The alteration in the In and Pt ratio readily varies the shape, size, and areal density of the resulting Pt NPs. The optical characteristics reveal that the localized surface plasmon resonance (LSPR) response is sensitively affected by the resulting surface morphology of Pt NPs. Specifically, the LSPR peak is dynamically tunable in the visible region over the range of wavelength 450 nm < lambda < 520 nm on the basis of the variation of the surface morphologies of Pt NPs. In contrast to the conventional dewetting of pure Pt films, this approach signifies the advantages such as improved configuration, uniformity, and isolation of Pt NPs under similar growth conditions. The growth characteristics and structures of the resulting Pt NPs are discussed on the basis of the enhanced diffusion, energy minimization, and equilibrium configuration mechanism.