Self-organization of random copolymers to nanopatterns by localized e-beam dosing

Abstract

Strategic electron beam (e-beam) irradiation on the surface of an ultrathin (<100 nm) film of polystyrene–poly(methyl methacrylate) (PS-PMMA) random copolymer followed by solvent annealing stimulates a special variety of dewetting, leading to large-area hierarchical nanoscale patterns. For this purpose, initially, a negative (positive) tone of resist PS (PMMA) under weak e-beam exposure is exploited to produce an array of sites composed of cross-linked PS (chain-scissioned PMMA). Subsequently, annealing with the help of a developer solvent engenders dewetted patterns in the exposed zones where PMMA blocks are confined by the blocks of cross-linked PS. The e-beam dosage was systematically varied from 180 μC cm−2 to 10 000 μC cm−2 to explore the tone reversal behavior of PMMA on the dewetted patterns. Remarkably, at relatively higher e-beam dosing, both PMMA and PS blocks act as negative tones in the exposed zone. In contrast, the chain scission of PMMA in the periphery of the exposed regions due to scattered secondary electrons caused confined dewetting upon solvent annealing. Such occurrences eventually lead to pattern miniaturization an order of magnitude greater than with conventional thermal or solvent vapor annealed dewetting. Selective removal of PMMA blocks of RCP using a suitable solvent provided an additional 50% reduction in the size of the dewetted features.

Electron-Beam Direct Writing-Based High-Performance Graphene Electrode Fabrication

“…The collisions between the incident electrons and the molecules of the precursor result in the kinetic energy transfer of electron to the precursor molecule and lead to their fragmentation; subsequently, the fragments cross-link and form a larger molecule with specific size distribution that is determined by both beam energy and dose. The whole process coincides with the typical process of overexposure of the positive photoresist . Additionally, the resistivity of the electrode rapidly decreases with the increase in the beam dose, but it will keep constant when the dose reaches or exceeds 1000 C/m 2 , as shown in Figure b.…”

“…The whole process coincides with the typical process of overexposure of the positive photoresist. 26 Additionally, the resistivity of the electrode rapidly decreases with the increase in the beam dose, 27 but it will keep constant when the dose reaches or exceeds 1000 C/m 2 , as shown in Figure 3b. The incident electrons induced high stress inside the resist, causing local plastic deformation.…”

Janus micro‐thread to micro‐nanodroplets using dynamic contact line lithography

“…from multiple polymers are explored. The motivation to construct these polymeric micro/ nanopatterns kindles from scientific urge as well as from practical applications such as resists, 18 smart adhesives, 19,20 optoelectronics, 21 magnetic media, 22 extraction using carbon-based nanohybrid materials, [23][24][25] substrates for preferential cell proliferation, 26 smart skins, 27,28 and so forth.…”