Localized conductive patterning via focused electron beam reduction of graphene oxide

Abstract

We report on a method for “direct-write” conductive patterning via reduction of graphene oxide (GO) sheets using focused electron beam induced deposition (FEBID) of carbon. FEBID treatment of the intrinsically dielectric graphene oxide between two metal terminals opens up the conduction channel, thus enabling a unique capability for nanoscale conductive domain patterning in GO. An increase in FEBID electron dose results in a significant increase of the domain electrical conductivity with improving linearity of drain-source current vs. voltage dependence, indicative of a change of graphene oxide electronic properties from insulating to semiconducting. Density functional theory calculations suggest a possible mechanism underlying this experimentally observed phenomenon, as localized reduction of graphene oxide layers via interactions with highly reactive intermediates of electron-beam-assisted dissociation of surface-adsorbed hydrocarbon molecules. These findings establish an unusual route for using FEBID as nanoscale lithography and patterning technique for engineering carbon-based nanomaterials and devices with locally tailored electronic properties.

Reductive nanometric patterning of graphene oxide paper using electron beam lithography

“…Such contrast would be expected as previous works using laser reduction have reported a thinning of the sample in the exposed area due to a more compact form of the reduced material [24]. However, in the literature, the thinning effect was not clearly visible in the topographic data in the case of electron exposure [44]. In this work, samples differ from others published, in that they have a much higher thickness than, e.g.…”

“…The dose used in area 5 is nearly the maximum possible to attain with the electron lithography tool, so images 2-5 in Figure 2 shows the largest effect that a focused 100 keV electron exposure can practically cause to the structure of GO paper. According to these results, for experiments performed in the range of 20 keV available in the literature [32,44], the depth of energy penetration is about 2 µm, which is adequate for the spin-coated thin films these authors used. With the incident energy of 100 keV used in the present work, the depth within which half of the energy is deposited is calculated to be 36 µm, a penetration depth similar to the thickness of the self-standing paper itself.…”

“…In parallel, others reported the reductive effect of electron beams, [43] and the lithographic writing of reduced patterns was reported using a 20 keV electron beam [32]. More recently, devices made of GO with micrometer scale reduced patterns have been produced using electron exposure at 25 keV [44].…”

“…Herein, we report the development of self-stained GO paper where direct-write EBL was used to create micrometer-scale conductive lines, using a 100 keV electron beam. To the best of our knowledge no studies were reported about GO reduction in the energy range used in this study, previous works used 20 keV [32] and 25 keV [44] for GO films, and 5 MeV [54] and 10 MeV [45] for GO paper.…”

Graphene Oxide Thin Films: Synthesis and Optical Characterization

“…Reduced GO (rGO) can be described as an reduced oxidized form of graphene, decorated mostly by hydroxyl, carboxyl and epoxy functional groups distributed randomly along the hexagonal sp 2 network of carbon atoms. [14][15][16][17] The oxygen functional groups of GO create sp 3 CÀ O sites; therefore, GO can be visualized as a two-dimensional network of sp 2 and sp 3 bonded atoms, in contrast to an ideal graphene sheet consisting of 100 % sp 2 carbon atoms. Graphene oxide is often described as an electrical insulator due to the presence of sp 3 CÀ O bonding; nevertheless, by reducing the CÀ O level, the sp 2 hybridization is restored and electrical conductivity is enhanced.…”