Driving forces for the self-assembly of graphene oxide on organic monolayers.

Johannes Kirschner,Christof M Jäger,Andreas Hirsch,Zhenxing Wang,Hans-Peter Steinrück,Timothy Clark,Marcus Halik,Siegfried Eigler

doi:10.1039/c4nr02527j

Abstract

Graphene oxide (GO) flakes were self-assembled from solution on surfaces of self-assembled monolayers (SAMs), varying in the chemical structure of their head groups. The coverage density of GO relates to strength of attractive interaction, which is largest for Coulomb interaction provided by positively charged SAM head groups and negatively charged GO. A rough surface enhances the coverage density but with the same trend in driving force dependency. The self-assembly approach was used to fabricate field-effect transistors with reduced GO (rGO) as active layer. The SAMs as attractive layer for self-assembly remain almost unaffected by the reduction from GO to rGO and serve as ultra-thin gate dielectrics in devices, which operate at low voltages of maximum 3 V and exhibit a shift of the Dirac voltage related to the dipole moment of the SAMs.

Highlights

Graphene-based electronics have achieved remarkable progress during the last decade since the successful isolation of a monolayer from graphite.[1,2] Due to the ultrahigh carrier mobility in the sp[2] carbon network of graphene akes, promising applications in high speed electronics and optoelectronics like frequency multipliers, mixers and photodetectors can be realized.[3,4,5,6,7] They are able to function on exible substrates due to the outstanding mechanical properties of graphene.[8,9] methods for producing large area graphene of high quality are available, the scalability of these methods is in need of improvement
The molecules of various chemical structures based on phosphonic acid (PA) are proven to form densely packed self-assembled monolayers (SAMs) and the utility of PA SAMs has been established as state-of-theart.[17,21]
We demonstrate a method for the site-selective deposition of graphene oxide (GO) on in-plane SAM patterns and SAMs on rough surfaces as FET gate pattern

Summary

Introduction

Graphene-based electronics have achieved remarkable progress during the last decade since the successful isolation of a monolayer from graphite.[1,2] Due to the ultrahigh carrier mobility in the sp[2] carbon network of graphene akes, promising applications in high speed electronics and optoelectronics like frequency multipliers, mixers and photodetectors can be realized.[3,4,5,6,7] They are able to function on exible substrates due to the outstanding mechanical properties of graphene.[8,9] methods for producing large area graphene of high quality are available, the scalability of these methods is in need of improvement. Hydrophilic/hydrophobic patterns of SAMs are used to selectively deposit GO.[13,14] By varying the head groups of the underlying SAM layer, different interaction forces (SAM-GO) can be provided and this leads to a method to tune the surface coverage of GO akes deposited from solution.

Results

Conclusion