Abstract
The localized surface plasmon resonance (LSPR) of noble metal nanoparticles (NPs) has become an important research topic in various fields and can be systematically tuned to obtain the desired device performance through the appropriate structural and elemental modifications. In this research, the improved LSPR properties of Pt NPs and diverse configurations and compositions of Ag–Pt bimetallic alloy NPs were demonstrated on sapphire (0001) via the solid-state dewetting (SSD) of Ag–Pt bilayers. A strong and dynamic LSPR response in the ultraviolet (UV) and visible (VIS) regions was demonstrated depending on the elemental composition and surface morphology of the NPs, which is discussed along with finite difference time domain (FDTD) simulations. In comparison, the Ag–Pt NPs exhibited stronger LSPR excitation, whereas the Pt NPs showed a relatively weaker and broader response. Meanwhile, the Pt NPs fabricated in this study still demonstrated a much-enhanced LSPR response compared to previous studies on the solid-state dewetting of pure Pt films due to improvements in configuration, uniformity, and interparticle gaps. Various surface morphologies of NPs, such as connected nanoclusters, elongated NPs, and isolated spherical NPs, were obtained on the basis of alloying, diffusion, Rayleigh instability, and a surface minimization mechanism, which were different from those of pure Ag and Pt NPs in similar growth conditions. Particularly, one-step annealing of an Ag–Pt bilayer yielded Ag–Pt alloy NPs below 600 °C, which subsequently transformed into pure Pt NPs above 650 °C, in which the high diffusivity and high vapor pressure of Ag atoms significantly facilitated the overall growth process of the NPs.
Highlights
Metallic nanoparticles (NPs) can exhibit various unique optical, electrical, chemical, electronic, and catalytic properties resulting from their strong surface plasmon resonance, high carrier concentration, photon–electron conversion, and high surface-to-volume ratio [1,2,3]
While these methods have been successfully demonstrated, the NPs produced are in the form of colloidal solutions, and many plasmonic and catalytic applications require the fabrication of alloy NP arrays that stably adhere to a substrate [18]
Due to the low diffusivity of Pt atoms, interconnected and irregular Pt NPs were fabricated with pure Pt thin films on sapphire even at an annealing temperature (Ta) above 800 ◦ C [23]
Summary
Metallic nanoparticles (NPs) can exhibit various unique optical, electrical, chemical, electronic, and catalytic properties resulting from their strong surface plasmon resonance, high carrier concentration, photon–electron conversion, and high surface-to-volume ratio [1,2,3]. These metallic NPs have been extensively adapted in a wide range of applications, such as in solar cells, catalysis, sensors, energy harvesting, and biomedical devices [4,5,6,7,8]. The integration of Ag and Pt into a single NP matrix can be an important research topic in realizing the improved plasmonic activity of Ag NPs as well as the chemical durability of Pt NPs, and this has not been reported in detail using the solid-state dewetting (SSD)
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