Inter-diffusion of plasmonic metals and phase change materials

Self Cite

Chalcogenide materials are attractive for all‐photonic phase‐change memories owing to their large optical contrast between amorphous and crystalline structural phases. However, high‐power heating pulses are required to switch these structural phases, which can limit the cyclability. To reduce power, Au nanoparticles (NPs) are embedded in a typical chalcogenide phase‐change material, Ge2Sb2Te5 (GST). Raman analysis shows that a GST film crystallizes at a low optical power of 2 mW, which is almost 10 times lower than that of materials not embedded with NPs. This lower power is owing to the enhanced light absorptance through the strongly localized surface plasmon resonance (LSPR) of the Au NPs. The Au NPs embedded in the GST film scatter light at λ = 587 nm, which is close to Au NP's LSPR of ≈535 nm. Laser light at 532 nm is used to measure Raman scattering from the Au–GST system. The Raman scattering is enhanced by a factor 12 compared with a bare GST film. This study indicates that the GST film–Au NP system is suitable for high‐speed, low‐power, phase‐change memory and for a new type of tunable surface‐enhanced Raman scattering substrate.

“…Furthermore, the Au NPs may be replaced by Ag or Al NPs that are low in cost and compatible with CMOS technology . Clearly, diffusion barriers would be necessary …”

Section: Resultsmentioning

confidence: 99%

Low‐Power Phase Transition of Chalcogenide Glass Using Au Nanoparticle Plasmon Resonance

Cao

Liu

et al. 2020

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“…PCMs have received a great deal of attention in the research area of active photonic devices . The main reason behind the selection of this multilayer combination is that many of the Ge 2 Sb 2 Te 5 (GST) tunable structures are not viable due to interdiffusion of noble metals with chalcogenides, when noble metals are in direct contact with chalcogenides . Unlink the PCM GST, Sb 2 S 3 has a bandgap of 2 eV, which renders it transmissive in the visible spectrum.…”

mentioning

confidence: 99%

Phase‐Change‐Material‐Based Low‐Loss Visible‐Frequency Hyperbolic Metamaterials for Ultrasensitive Label‐Free Biosensing

Sreekanth

Ouyang

Sreejith

et al. 2019

Self Cite

The extreme anisotropic permittivity of hyperbolic metamaterials (HMMs) represent a unique opportunity to realize effective bulk metastructures with extraordinary optical properties over a broad frequency range from visible to terahertz. [1] HMMs are artificial uniaxial materials that exhibit hyperbolic dispersion because the out of plane dielectric constant (ε zz = ε ⊥ ) has an opposite sign to the in-plane dielectric constants (ε xx = ε yy = ε ll ). HMMs can be classified into two types based on the sign of their dielectric components, i.e., type I (−ε ⊥ and ε ll ) and type II (ε ⊥ and −ε ll ). In comparison to isotropic materials showing elliptical dispersion, HMMs support propagation of optical modes across the structure with infinitely large momentum (high-k modes) in the effective medium limit, [2,3] irrespective of Hyperbolic metamaterials (HMMs) have emerged as a burgeoning field of research over the past few years as their dispersion can be easily engineered in different spectral regions using various material combinations. Even though HMMs have comparatively low optical loss due to a single resonance, the noble-metal-based HMMs are limited by their strong energy dissipation in metallic layers at visible frequencies. Here, the fabrication of noble-metal-free reconfigurable HMMs for visible photonic applications is experimentally demonstrated. The low-loss and active HMMs are realized by combining titanium nitride (TiN) and stibnite (Sb 2 S 3 ) as the phase change material. A reconfigurable plasmonic biosensor platform based on active Sb 2 S 3 -TiN HMMs is proposed, and it is shown that significant improvement in sensitivity is possible for small molecule detection at low concentrations. In addition, a plasmonic apta-biosensor based on a hybrid platform of graphene and Sb 2 S 3 -TiN HMM is developed and the detection and real-time binding of thrombin concentration as low as 1 × 10 −15 m are demonstrated. A biosensor operating in the visible range has several advantages including the availability of sources and detectors in this region, and ease of operation particularly for point-of-care applications.

“…By contrast, further reversible transition from the crystalline state to the amorphous state usually requires a short pulse of electric or optical energy, proper buffer and capping layers, which need to be considered in the design of metasurfaces. A recent study also shows the interdiffusion between metal atoms and GST. Therefore, barrier layers such as Si 3 N 4 or TiN are suggested to use when incorporating GST with plasmonic metasurfaces.…”

Section: Properties Of Phase‐change Chalcogenidesmentioning

confidence: 83%

Dynamic Metasurfaces Using Phase‐Change Chalcogenides

Ding

Yang

Bozhevolnyi

2019

180

134

Metasurfaces have attracted increasing attention and provide promising solutions for cost‐effective and highly efficient optics due to their unprecedented capabilities in light manipulation. In recent years, phase‐change materials (PCMs), especially phase‐change chalcogenides, are integrated into metasurfaces to explore innovative configurations exhibiting remarkable tunability and reconfigurability due to the dramatic optical contrasts available in PCMs along with their high chemical and long‐term stability and high switching speeds. In this review, the current achievements and ongoing developments in dynamic metasurfaces based on phase‐change chalcogenides, an emerging field in nanophotonics and optoelectronics, are outlined. Starting with the basic material properties of phase‐change chalcogenides, the structural transformations and dielectric functions of two main chalcogenides are described. This is followed by an overview of the main progress in typical dynamic metasurfaces based on phase‐change chalcogenides enabling global and local amplitude/phase modulation. The review ends with a short conclusion and outlook on possible future developments.