Ultrathin phase-change coatings on metals for electrothermally tunable colors

Abstract

Metal surfaces coated with ultrathin lossy dielectrics enable color generation through strong interferences in the visible spectrum. Using a phase-change thin film as the coating layer offers tuning the generated color by crystallization or re-amorphization. Here, we study the optical response of surfaces consisting of thin (5–40 nm) phase-changing Ge2Sb2Te5 (GST) films on metal, primarily Al, layers. A color scale ranging from yellow to red to blue that is obtained using different thicknesses of as-deposited amorphous GST layers turns dim gray upon annealing-induced crystallization of the GST. Moreover, when a relatively thick (>100 nm) and lossless dielectric film is introduced between the GST and Al layers, optical cavity modes are observed, offering a rich color gamut at the expense of the angle independent optical response. Finally, a color pixel structure is proposed for ultrahigh resolution (pixel size: 5 × 5 μm2), non-volatile displays, where the metal layer acting like a mirror is used as a heater element. The electrothermal simulations of such a pixel structure suggest that crystallization and re-amorphization of the GST layer using electrical pulses are possible for electrothermal color tuning.

Functional Charge Transfer Plasmon Metadevices

“…Similar to the full gold case, a dipolar mode is appeared at higher energies, while a pronounced dipolar extreme is observed around 1.7 μm, owing to the strong capacitive coupling between gold nanorods. Moreover, when the gap area is filled up with GST (initially, considered as a-GST), the dipolar peak around 1.7 μm is red-shifted to 2.2 μm with slightly increased intensity, due to negligible extinction coefficient (k~0) of the a-GST in this regime [138]. Once the phase of the GST become fully crystallized (c-GST), its corresponding resistivity value decreases 6 orders of magnitude and the charge flow starts to dominate the spectral response of the system.…”

Metasurface Color Filters Using Aluminum and Lithium Niobate Configurations

“…Most of designs are in the IR [10][11][12][25][26][27] and THz [28][29][30][31] spectral ranges. Although there have been various reported approaches for actively tunable metasurfaces in the visible spectral range, such as mechanical stretching [32], electrostatic force [33], Mie resonance [34], liquid crystal [35], phase change material [36][37][38], and electrooptic material [39,40] However, the number of studies on actively tunable metasurfaces in the visible spectral range is limited. Among the tuning mechanisms of electro-optical methods, graphene-based tunable metasurface recently draws a massive attention to researchers [41][42][43].…”

Tailoring active color rendering and multiband photodetection in a vanadium-dioxide-based metamaterial absorber

“…While the rendering colors of the designed devices can represent the working state in the other spectra, like a pH indicator, it will therefore enhance efficiency and cost effectiveness. Phase-change materials exhibit broadband electromagnetic response with tunable properties, such as germanium-antimony-tellurium alloys (Ge 2 Sb 2 Te 5 ) [25][26][27][28], and vanadium dioxide (VO 2 ) [29], which could be excellent candidates for multiband and multifunctional applications. VO 2 , an iconic example of a correlated electron material, has received significant attention because of its insulating-metallic transition (IMT) at ∼68°C [30,31].…”