Thursday, March 10, 2016

Atomic Layer Lithography turns ALD into an angstrom-resolution gap-forming method

Here is a really cool paper on Atomic Layer Lithography! The method is a combination of "atomic layer lithography, which turns atomic layer deposition (ALD) into an angstrom-resolution gap-forming method" The combination of these two powerful methods can create ultrasmall coaxial nanocavities at extreme densities over an entire wafer, opening up the door to devices with sub-10 nm gaps"

High-Throughput Fabrication of Resonant Metamaterials with Ultrasmall Coaxial Apertures via Atomic Layer Lithography

Daehan Yoo, Ngoc-Cuong Nguyen, Luis Martin-Moreno, Daniel A. Mohr, Sol Carretero-Palacios, Jonah Shaver, Jaime Peraire, Thomas W. Ebbesen, and Sang-Hyun Oh

Nano Lett., 2016, 16 (3), pp 2040–2046 DOI: 10.1021/acs.nanolett.6b00024

Figure from graphical abstract used with permission (Account #: 3000915597)
We combine atomic layer lithography and glancing-angle ion polishing to create wafer-scale metamaterials composed of dense arrays of ultrasmall coaxial nanocavities in gold films. This new fabrication scheme makes it possible to shrink the diameter and increase the packing density of 2 nm-gap coaxial resonators, an extreme subwavelength structure first manufactured via atomic layer lithography, both by a factor of 100 with respect to previous studies. We demonstrate that the nonpropagating zeroth-order Fabry-Pérot mode, which possesses slow light-like properties at the cutoff resonance, traps infrared light inside 2 nm gaps (gap volume ∼ λ3/106). Notably, the annular gaps cover only 3% or less of the metal surface, while open-area normalized transmission is as high as 1700% at the epsilon-near-zero (ENZ) condition. The resulting energy accumulation alongside extraordinary optical transmission can benefit applications in nonlinear optics, optical trapping, and surface-enhanced spectroscopies. Furthermore, because the resonance wavelength is independent of the cavity length and dramatically red shifts as the gap size is reduced, large-area arrays can be constructed with λresonance ≫ period, making this fabrication method ideal for manufacturing resonant metamaterials.