Optoelectronic properties of graphene thin films deposited by a Langmuir–Blodgett assembly

Abstract

Large area thin films of few-layered unfunctionalized graphene platelets are developed with fine control over the thickness. The thin films are obtained by a Langmuir-Blodgett assembly at the interface of graphene solution in N-methyl-2-pyrrolidone (NMP) and water, and their optoelectronic properties and conduction mechanism are investigated in relation to lateral flake size and thin film thickness. The electrical conductivity and carrier mobility are affected by the flake size (200 nm to 1 μm) and by the packing of the nanostructure platelet network. General effective medium theory is used to explain the thickness dependent conductivity and to determine the percolation threshold film thickness which was found to be about 10 nm (at a volume fraction of ~39%) for a Langmuir-Blodgett film of an average platelet lateral size of 170 ± 40 nm. The electronic behaviour of the material shows more similarities with polycrystalline turbostratic graphite than thin films of reduced graphene oxide, carbon nanotubes, or disordered conducting polymers. While in these systems the conduction mechanism is often dominated by the presence of an energy barrier between conductive and non-conductive regions in the network, in the exfoliated graphene networks the conduction mechanism can be explained by the simple two-band model which is characteristic of polycrystalline graphite.

Nonvolatile Memories Based on Graphene and Related 2D Materials

“…Moreover, the possibility of having a large class of solution‐processed 2D materials enables their integration with polymeric materials or deposition/coating on different substrates. In this context, progress on large‐scale placement of 2D materials–based inks by the various deposition/coating techniques such as Langmuir–Blodgett, spin‐, spray‐ and rod‐coating, and inkjet printing, is enabling printing of 2D materials–based films and heterostructures on a large scale . Nonetheless, apart from the uniformity of large‐area films, the roughness of the deposited film is still an issue for both optical and electronic properties of the deposited films and worse than those obtained by micromechanical cleavage or the direct growth.…”

Production and Patterning of Liquid Phase–Exfoliated 2D Sheets for Applications in Optoelectronics

“…Hitherto, exfoliated graphene[64b,68,160] and BP have been organized into LB films. Kim et al[160a] reported on the formation of LB films from graphene/NMP dispersion.…”

A Multifunctional Polymer-Graphene Thin-Film Transistor with Tunable Transport Regimes

“…On the one hand, liquidphase exfoliation of graphite into graphene is emerging as a suitable up-scalable method for the production of high quality graphene. [5][6][7][8][9] On the other hand, different strategies have been proposed in order to open a band gap in graphene such as the production of reduced graphene oxide 10,11 or graphene nanoribbons. [12][13][14][15][16] A different way of employing graphene for electronics relies on the use of hybrid solutions that combine graphene with suitable molecules to enable reciprocal modification of the component properties, e.g.…”