A New Strategy of Lithography Based on Phase Separation of Polymer Blends

Abstract

Herein, we propose a new strategy of maskless lithographic approach to fabricate micro/nano-porous structures by phase separation of polystyrene (PS)/Polyethylene glycol (PEG) immiscible polymer blend. Its simple process only involves a spin coating of polymer blend followed by a development with deionized water rinse to remove PEG moiety, which provides an extremely facile, low-cost, easily accessible nanofabrication method to obtain the porous structures with wafer-scale. By controlling the weight ratio of PS/PEG polymer blend, its concentration and the spin-coating speed, the structural parameters of the porous nanostructure could be effectively tuned. These micro/nano porous structures could be converted into versatile functional nanostructures in combination with follow-up conventional chemical and physical nanofabrication techniques. As demonstrations of perceived potential applications using our developed phase separation lithography, we fabricate wafer-scale pure dielectric (silicon)-based two-dimensional nanostructures with high broadband absorption on silicon wafers due to their great light trapping ability, which could be expected for promising applications in the fields of photovoltaic devices and thermal emitters with very good performances, and Ag nanodot arrays which possess a surface enhanced Raman scattering (SERS) enhancement factor up to 1.64 × 108 with high uniformity across over an entire wafer.

Bioinspired phase-separated disordered nanostructures for thin photovoltaic absorbers

“…The lithography technique relies on the phase separation of two nonmiscible polymers in a blend solution during a spin-coating process (see Materials and Methods for details). Multisize nanohole patterns with controllable size distribution and ff were thus obtained ( 50 , 51 ). Afterward, the nanoholes were transferred into a 130-nm-thick a-Si:H layer by RIE using the patterned resist layer as an etching mask.…”

“…In comparison to other bottom-up techniques, for example, colloidal lithography for similar nanostructures, phase separation of binary polymer blends via spin coating offers great flexibility because the hole distribution can be easily tailored by adjusting the processing parameters. For example, by regulating the mass ratio between PS and PMMA, their molecular chain length, the spin-coating parameters with solvent concentration and humidity during spin coating, the hole distribution, and the ff can be tuned in a wide range ( 50 , 51 , 56 ). Moreover, the proposed technique does not require the evaporation of a metal film as an etching mask to transfer the pattern into the a-Si:H slab ( 33 , 57 , 58 ).…”

Realistic Silver Optical Constants for Plasmonics

“…Silver is predominantly the preferred material for applications in extraordinary optical transmission 1 2 3 , near-field and coherent microscopy 4 5 6 7 , far-field superlensing 8 9 , single photon emission 10 and photovoltaic absorption-enhancement 2 11 12 13 . Almost invariably, simulations use Ag optical data from Palik’s 1985 handbook 14 or, more commonly, an earlier Johnson and Christy (J&C) tabulation 15 .…”

Single Solvent‐Based Film Casting Method for the Production of Porous Polymer Films

“…Porous films are traditionally fabricated by breath figure, polymerization, sol–gel, sacrificial templates, and photolithography processes . Most of these production processes have lengthy and/or complicated manufacturing processes and can use several types of sacrificial materials and/or solvents .…”