Self-Assembly Based Plasmonic Arrays Tuned by Atomic Layer Deposition for Extreme Visible Light Absorption

Abstract

Achieving complete absorption of visible light with a minimal amount of material is highly desirable for many applications, including solar energy conversion to fuel and electricity, where benefits in conversion efficiency and economy can be obtained. On a fundamental level, it is of great interest to explore whether the ultimate limits in light absorption per unit volume can be achieved by capitalizing on the advances in metamaterial science and nanosynthesis. Here, we combine block copolymer lithography and atomic layer deposition to tune the effective optical properties of a plasmonic array at the atomic scale. Critical coupling to the resulting nanocomposite layer is accomplished through guidance by a simple analytical model and measurements by spectroscopic ellipsometry. Thereby, a maximized absorption of light exceeding 99% is accomplished, of which up to about 93% occurs in a volume-equivalent thickness of gold of only 1.6 nm. This corresponds to a record effective absorption coefficient of 1.7 × 10(7) cm(-1) in the visible region, far exceeding those of solid metals, graphene, dye monolayers, and thin film solar cell materials. It is more than a factor of 2 higher than that previously obtained using a critically coupled dye J-aggregate, with a peak width exceeding the latter by 1 order of magnitude. These results thereby substantially push the limits for light harvesting in ultrathin, nanoengineered systems.

Optical interactions in plasmonic nanostructures

“…Again, the implementation of this concept requires an artificial composite medium made of plasmonic nanostructures. Recently, strong absorption has been experimentally observed using a gold nanoparticle array fabricated by block copolymer lithography and overcoated with a dielectric layer by atomic layer deposition [70]. As shown in Figure 4, the ultrathin composite film with a thickness of~25 nm exhibited near-perfect absorption at around 600 nm.…”

Scalable residue-free graphene for surface-enhanced Raman scattering

“…The optical properties of Au were modeled with surface scattering contributions taken into account. [28] Under the cylinders, PMMA, SLG, 300 nm SiO 2 and Si were stacked. The graphene was modeled as a 0.34 nm thick layer with a fixed n = 3 and an extinction coefficient varying according to k = 1.82λ where λ is the wavelength in µm.…”

Impact of Atomic Layer Deposition to Nanophotonic Structures and Devices

“…Likewise, Sung et al (2008) showed enhanced thermal stability of Al 2 O 3 coated silver nanoparticles against high power femtosecond laser. Self-assembly based plasmonic arrays tuned by minimum thickness of ALD fabricated (<20 nm) Au dots achieved enhanced visible light absorption per volume-equivalent thickness Frontiers in Materials | Thin Solid Films in applications including conversion of solar energy into electrical power (Hägglund et al, 2013). One of the possible reason of enhancing optical transmission is conformal and precisely uniform deposition of dielectric thin films on nano-structures is its predominance over rough topographies.…”