Squeezing Bulk Plasmon Polaritons through Hyperbolic Metamaterials for Large Area Deep Subwavelength Interference Lithography

Abstract

Hyperbolic metamaterial composed of SiO 2 /Al fi lms are explored to squeeze out bulk plasmon polaritons (BPPs) to produce large area and uniform deep subwavelength interference patterns. As examples, two and four BPPs interference lithography with half pitch 45 nm (≈ λ /8) are demonstrated in experiments. Much deeper resolution up to 22.5 nm (≈ λ /16) and variety of BPPs interference patterns are feasible. The period of grating structures for transferring photons to BPPs is much larger than that of BPPs interference patterns, facilitating the structures fabrication by simple and low cost methods like large area laser interference lithography. It is believed that the method provides a cost-effective, parallel, and large area nanofabrication way.

Principles of electromagnetic waves in metasurfaces

“…This can also be utilized to filter the evanescent wave, achieve higher resolution and better imaging quality [26,49]. Recently, this multilayered structure has been utilized to achieve subdiffraction directive propagation of SPP [50].…”

“…At specific case, effective parameters can be obtained using effective medium theory. For the two electric fields polarized parallel and perpendicular to the multilayers, the effective permittivity can be written as [46][47][48][49]:…”

Achieving pattern uniformity in plasmonic lithography by spatial frequency selection

“…The transmitted diffraction orders interfere and produce uniform periodic patterns in the PR film. As an example, we use the work reported in reference [18] and design the corresponding stacked HMM to pass the ±second-order diffracted waves of the grating. To produce a similar pattern size as in the superlens case, a grating type Cr mask is used with the period of 360 nm (i.e.…”

“…In other works, a stacked metal/dielectric multilayer structure was proposed to obtain super-resolution by various means including spherical hyperlens [15,16] and negative refraction [17]. Especially, a hyperbolic metamaterial (HMM)-based structure can be designed as a filter to allow waves with high spatial frequency to pass through, and suppress other spatial frequencies [18]. Because thin metallic and dielectric films are required to achieve efficient coupling between the SPs at each metal and dielectric interface, similar questions regarding the impacts of the roughness of the mask or the thin film on the pattern quality are raised.…”

Color display and encryption with a plasmonic polarizing metamirror

“…Electron-beam lithography (EBL) and focused ion-beam milling (FIB) offer the platform to fabricate such nanostructures with small separations; however, these methods are expensive and inefficient. Interference lithography, which provides a cost-effective approach to manufacture large-area mass-production periodic nanostructures, is adopted in our work and expected to achieve ultrasmooth silver grating combined with strip-off technology [26].…”