Electron-Beam Irradiation of Cinnamate Films Affords Nanoscale Patterned Substrates for Use in Devices and as Scaffolds in Tissue Engineering

Abstract

The fabrication of electronic, photonic, and metamaterial-based devices, or tissue engineering requires the controlled deposition and patterning of materials. Electron-beam lithography (EBL) offers unprecedented miniaturization of those devices because of its high resolution. We present a concept to induce a classic photochemical reaction in condensed matter via EBL. We investigate the response of a tetrameric cinnamate monomer in thin films toward photon and electron radiation. In the solid state, photoexcitation and electron bombardment similarly induce [2 + 2] cycloadditions, forming insoluble truxilic acid esters, as shown via IR spectroscopy measurements. Subsequently, we employed the investigated material as an electron-beam resist, showing resistance against wet-chemical etchants. Structures with resolution down to 60 nm were obtained, not achievable with conventional photolithography, proving that [2 + 2] cycloaddition of cinnamic acid containing compounds is suitable for applications in the field of EBL.

Electron-beam lithography of cinnamate polythiophene films: conductive nanorods for electronic applications

“…2 and S7 † ). 24,31 IR spectra of UV-immobilized films (Fig. S6 † ) are superimposable to those obtained after EB treatment, indicating similar or identical reactivity under both types of irradiation.…”

“…In contrast to small molecules previously reported, a lower cross-linking degree suffices to induce polymer immobilization through network formation. 24 Surface charging additionally limits the resolution. 70 nm is achievable at a dose of 2.5 mC cm −2 (ESI, Fig.…”

“…2 and S7 †). 24,31 IR spectra of UVimmobilized lms (Fig. The lm retention curves describing dose-dependent lm thicknesses aer development (ESI, Fig.…”

“…22,23 Recently, we "photo"-crosslinked a tetracinnamate-based monomer by highenergy electron radiation (10 keV) triggering the [2+2] cycloaddition. 24 Robust nanostructures (resolution 60 nm) resist wetchemical etching. The electron beam induced crosslinking is mechanistically similar to that of photoreactions of cinnamates, 23,24 as summarized in Fig.…”

“…24 Robust nanostructures (resolution 60 nm) resist wetchemical etching. The electron beam induced crosslinking is mechanistically similar to that of photoreactions of cinnamates, 23,24 as summarized in Fig. 1b.…”