Controlling the Physicochemical State of Carbon on Graphene Using Focused Electron-Beam-Induced Deposition

Abstract

Focused electron-beam-induced deposition (FEBID) is a promising nanolithography technique using "direct-write" patterning by carbon line and dot deposits on graphene. Understanding interactions between deposited carbon molecules and graphene enables highly localized modification of graphene properties, which is foundational to the FEBID utility as a nanopatterning tool. In this study, we demonstrate a unique possibility to induce dramatically different adsorption states of FEBID-produced carbon deposits on graphene, through density functional theory calculations and complementary Raman experiments. Specifically, an amorphous carbon deposit formed by direct irradiation of high energy primary electrons exhibits unusually strong interactions with graphene via covalent bonding, whereas the FEBID carbon formed due to low-energy secondary electrons is only weakly interacting with graphene via physisorption. These observations not only are of fundamental importance to basic physical chemistry of FEBID carbon-graphene interactions but also enable the use of selective laser-assisted postdeposition ablation to effectively remove the parasitically deposited, physisorbed carbon films for improving FEBID patterning resolution.

Localized conductive patterning via focused electron beam reduction of graphene oxide

“…While kinetic energy of methane plasmas can facilitate reduction reactions with graphene oxide during plasma treatment, direct irradiation of electrons during FEBID can influence such reactions of dissociated species with functional groups of graphene oxide, which helps to overcome activation energies necessary for the reaction of highly reactive species with graphene oxide, similar to promoting chemisorption of FEBID intermediate species on graphene. 15,29 Furthermore, the removal of functional groups and reduction of O:C ratio in GO via FEBID treatment are in a good agreement with the recently reported XPS results about the reduction of graphene oxide by irradiating high energy (10 MeV) electrons. 30 Collectively, the DFT calculations and the relevant experimental results from the literatures provide a strong support for graphene oxide chemical modification/ reduction facilitated by FEBID carbon deposition as a primary mechanism responsible for an increase of the local GO electrical conductivity and transition from its insulating to semiconducting behavior by FEBID treatment, as observed in our experiments upon an increase in the electron irradiation dose (Fig.…”

“…11-14 FEBID process involves interactions of primary electrons and adsorbed precursor molecules with a supporting dielectric or conductive substrate, affecting the deposition outcomes. 12,15,16 Additionally, electron beam irradiation of graphene was shown to modify electronic properties of graphene (e.g., shift the Dirac point) 17 as well as its chemical properties (e.g., strength of interactions with adsorbed species) by introducing structural defects into the 2D material structure. 15 Therefore, there is an intriguing opportunity to modify the electronic properties of graphene oxide via application of a FEBID technique to enable the localized, high-resolution, controllable patterning for realization of interesting electronic functionalities.…”

“…24 Self-consistent field (SCF) convergence, 10 À5 Ha, was obtained at 9 Â 9 Â 1 Monkhorst-Pack (MP) k-point grid. 15 For modeling graphene oxide, only epoxide and hydroxyl species were considered as surface functionalities of graphene oxide. The graphene oxide structure in Fig.…”

Dynamic modulation of electronic properties of graphene by localized carbon doping using focused electron beam induced deposition

“…18,19 Its capability of controllable, nano-scale patterning of carbon materials on graphene provides an intriguing opportunity to modify graphene's properties. [21][22][23] Specifically, FEBID can induce strong chemical binding of deposited amorphous carbon with graphene carbon atoms, leading to generation of sp 3 -type defects on graphene. 14,15 It was suggested to be due to generation of defects in graphene and modification of a supporting dielectric substrate via interaction with the electron beam.…”

“…20,21 Direct exposure of high energy electrons to an entire area of a graphene conduction channel is known to result in increase of device electrical resistance and induce n-type doping. 21 In order to explore the effect of carbon deposition on electronic properties of a graphene conduction channel, we introduced localized carbon deposits on the graphene conduction channel, controlled by changing primary electron beam dose irradiated onto source and drain metal contacts. However, carbon deposition on graphene has not been considered even though carbon can be easily formed during electron beam exposure, significantly affecting structural (compositional) properties of graphene.…”