Direct-Write Fabrication of Cellulose Nano-Structures via Focused Electron Beam Induced Nanosynthesis.

Thomas Ganner,Bernhard Rumpf,Jürgen Sattelkow,Bernd Nidetzky,David Reishofer,Stefan Spirk,Robert Winkler,Harald Plank,Manuel Eibinger

doi:10.1038/srep32451

Abstract

In many areas of science and technology, patterned films and surfaces play a key role in engineering and development of advanced materials. Here, we introduce a new generic technique for the fabrication of polysaccharide nano-structures via focused electron beam induced conversion (FEBIC). For the proof of principle, organosoluble trimethylsilyl-cellulose (TMSC) thin films have been deposited by spin coating on SiO2 / Si and exposed to a nano-sized electron beam. It turns out that in the exposed areas an electron induced desilylation reaction takes place converting soluble TMSC to rather insoluble cellulose. After removal of the unexposed TMSC areas, structured cellulose patterns remain on the surface with FWHM line widths down to 70 nm. Systematic FEBIC parameter sweeps reveal a generally electron dose dependent behavior with three working regimes: incomplete conversion, ideal doses and over exposure. Direct (FT-IR) and indirect chemical analyses (enzymatic degradation) confirmed the cellulosic character of ideally converted areas. These investigations are complemented by a theoretical model which suggests a two-step reaction process by means of TMSC → cellulose and cellulose → non-cellulose material conversion in excellent agreement with experimental data. The extracted, individual reaction rates allowed the derivation of design rules for FEBIC parameters towards highest conversion efficiencies and highest lateral resolution.

Highlights

With other biomolecules such as proteins, DNA and other polysaccharides and allowed for investigations into the interaction of cellulose with water[10,11,12,13,14,15,16,17,18,19,20,21]
TMSC regeneration is achieved by use of acidic or basic reagents which catalyze the de-silylation of TMSC into cellulose via hydrophilic attack at the central silicon atom
We denote the process as Focused Electron Beam Induced Conversion (FEBIC) and provide a detailed process parameter study and its conversion implications in the following

Summary

Introduction

With other biomolecules such as proteins, DNA and other polysaccharides and allowed for investigations into the interaction of cellulose with water[10,11,12,13,14,15,16,17,18,19,20,21]. The large feature size and traces of remaining NHNA might be detrimental for specific applications Another approach to produce larger patterns within short times was introduced by Taajamaa et al.[27] by using a polysaccharid/polysterene blend. A recent study by Taskei et al.[37] which used a different cellulose based resist material showed that electron lithography on cellulose-derivates is a feasible method to fabricate, e.g., nanostructured masks for semiconductor industry and demonstrates the significance for industry Based on this motivation, we here demonstrate a highly localized, direct conversion of TMSC layers into cellulose via a nano-sized focused electron beam as used in classical scanning electron microscopes (SEM). The final part focuses on the downscaling which reveals that this method is capable to produce cellulose structures in the sub−100 nm regime via this direct write conversion approach

Methods

Results

Conclusion