An Omnidirectional Transparent Conducting‐Metal‐Based Plasmonic Nanocomposite

Abstract

The task to produce a transparent metal, with conductivity comparable to indium tin oxide (ITO) while retaining high transparency through the visible region has so far proven to be challenging. In this regard, metal-polymer nanocomposites have traditionally been excluded from investigation due to their strong absorption and refl ection of visible light. Here, we present the fi rst transparent conducting metal (TCM) composed of a stack of a gold fi lm and a silver/polymer nanocomposite fabricated by sputtering on a glass substrate. In this plasmonic device, the refl ection is minimized by means of symmetric plasmonic coupling under impedance matching condition in the visible range. Additionally the magnetic optical resonance, which is induced by dipole-image interaction lowers the absorption and scattering of the whole structure. Since both phenomena occur in the same wavelength range, the optical transmission of the device is signifi cantly enhanced. The plasmonic metamaterial shows an omnidirectional optical transmission up to 80% in the visible wavelength range, which is comparable to that of ITO, and an electrical conductivity that is one order of magnitude higher than that of ITO.In the fi eld of plasmonics, much attention is paid to new approaches for the concentration and manipulation of light to improve the absorption and/or transmission of energy. [ 1 ] For instance, a combination of noble metal nanoparticles and a metal fi lm has been used to diminish the refl ection by plasmonic coupling. [ 2 ] Applying the same idea, recently a perfect absorber was realized with a structure consisting of a gold metal fi lm separated from gold nanoparticles with MgF 2 as an interlayer. [ 3 ] Other plasmonic devices, which show high absorbance, were fabricated by structuring a metal surface in different manners such as a nanostructure layer [ 4 ] or microcavities on the top surface. [ 5 ] Light propagation normal to the metal fi lm is an interesting issue. When the fi lm is optically thin, i.e., in the range of the skin depth, the energy transfer can be enhanced by the surface plasmon polariton (SPP) mode and super-resolution imaging can be achieved. [ 6 ] These unique features have generated the rapidly growing fi eld of SPP-based photonics or plasmonics. Plasmonics combines both the capacity of photonics and the miniaturization capability of electronics and is thus an outstanding candidate for future optoelectronic applications. [ 7 ] Transparent conductors (TCs), which are integral components in fl at panel displays, solar cells, and smart windows, deliver electrons to or collect them from the active part of the device while at the same time allowing visible photons to pass through relatively unimpeded. At present, ITO and other transparent conductive oxides (TCO) are used. Efforts to produce a transparent metal with conductivity superior to ITO that retains high transparency through the visible region has so far proved to be challenging. [ 8 ] Metal/polymer nanocomposites, which show some attractive optical propertie...

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