Tunable Optical Response Based on Au@GST Core–Shell Hetero-nanostructures

Abstract

Active control over the optical response has been investigated extensively, which is highly required in next-generation photonic devices. Here, we report a core−shell nanostructure combined with the plasmonic nanostructure with an active phase change material, termed as Au@GST, where the individual Au nanoparticle is wrapped by isolated active Ge 2 Sb 2 Te 5 (GST) tuning medium as the shell. We demonstrate the active control of optical response by the simultaneous control of size and crystallization degree of the phase change shell within each isolated core−shell nanostructure. The hetero-nanostructures are synthesized by direct sputtering of stoichiometric GST on Au nanoparticles with different sizes based on a seeding effect of the metal nanostructures. The tunable optical response is enabled by inducing the GST shell phase states between amorphous and crystalline phases through thermal annealing, accompanied by high optical contrast. We demonstrate the tunable optical response (from 570 to 630 nm) of the hetero-nanostructures by tailoring the GST shell's optical property. The experimental results show that the optical response of the Au@GST core−shell hetero-nanostructures exhibits high sensitivity to the size of the nanoparticles (GST thickness and Au diameter). The simulation results are in good agreement with the experiments. This confirms the dominant role of the phase states on the optical modulation. Furthermore, this study provides a single-step and lithography-free 3D printing process to arrange the hybrid Au@GST core−shell nanostructures in a large area deliberately, giving additional flexibility to control over the architecture and geometry. Such Au@GST core−shell hetero-nanostructures have the potential for active control of nanophotonic devices, such as super-resolution imaging and programmable metasurfaces.

In Situ Monitoring of Scale Effects on Phase Selection and Plasmonic Shifts during the Growth of AgCu Alloy Nanostructures for Anticounterfeiting Applications

“…We are able to deduce mobility coefficients for Ag, Cu, and Ag 42 Cu 58 alloy clusters. TEM is a well-established method for investigating Cu–Ag nanoalloy structures. − Our results show quantitative agreement with MD simulations from Bonitz et al Based on the knowledge on the nanoscale dynamics, the plasmon resonance shift induced by morphological changes is quantified, which makes it useful for anticounterfeiting based on nanoscale heterostructures. , …”

“…The tuning of plasmon resonances has important applications in biosensor devices − and photovoltaics , because the plasmon resonance strongly depends on the cluster size, arrangement, the materials used, and their composition . Especially the use of bimetallic alloys allows for fine-tuning of the plasmon resonance, which offers new pathways in anticounterfeiting: in combination with polymer supports and templates, structural color can readily be achieved by exploiting the plasmon resonance. ,− Moreover, this enables fast electrochromic color switching of smart windows . Hence, understanding the correlation of size and composition with the plasmonic and optoelectronic behavior of polymer-supported metal cluster systems carries high potential but also is a challenge.…”

“…48−50 Our results show quantitative agreement with MD simulations from Bonitz et al 46 Based on the knowledge on the nanoscale dynamics, the plasmon resonance shift induced by morphological changes is quantified, which makes it useful for anticounterfeiting based on nanoscale heterostructures. 12,51 ■ EXPERIMENTAL SECTION Materials. Thin PMMA films were spin-coated with a thickness of (80 ± 5) nm.…”