Graphitization at interface between amorphous carbon and liquid gallium for fabricating large area graphene sheets

Abstract

We have found that liquid gallium exhibits as a good graphitizing catalyst for a large area graphene sheet. While gallium and carbon are known to be an insoluble system, however, we have found that the catalytic reaction occurs at a very narrow interfacial region between amorphous carbon and liquid gallium. Amorphous carbon film was transformed into graphite layer composed of a few layers of graphene sheet. These thin graphene film can be easily transferred into silicon substrate through the intermediation of PDMS rubber stamping.

Preparation and Characterization of Biobased Graphene from Kraft Lignin

“…Other biomass materials are potential solid carbon sources for graphene fabrication. Graphene growth can be initiated by metal catalysts (Fujita et al 2009;Juang et al 2009;Rodríguez-Manzo et al 2011). The operation is simple, but the purity is low.…”

Kinetics of Ga droplet decay on thin carbon films

“…In contrast with previous in situ TEM observations, we do not observe graphitic shell formation around the droplets. 19,21,22,24 We do, however, observe small remnants that do not change in size after the bulk of the droplets dissolve. While the images lack sufficient resolution to identify these features, presumably they are graphitic shells as has been reported in the literature.…”

“…Energy dispersive spectroscopy (EDS) measurements acquired from the XTEM sample, both before and after annealing, indicate that a significant amount of Ga was present within the carbon film prior to heating and in the droplets observed post-annealing after air-exposure. EDS data also indicated a significant fraction of oxygen but this is likely due to air exposure and not expected in the droplets since gallium oxide does not melt at 773 K. The presence of carbon, if any, 19,[21][22][23] within the droplets could not be determined accurately from EDS due to the large background signal of carbon from the surrounding region. This procedure of forming Ga droplets is highly reproducible and we have obtained similar results, i.e., Ga droplets on carbon films on FIB-prepared XTEM samples of C/Ti/Si, Zr/Al 2 O 3 (0001), and bare Al 2 O 3 (0001) substrates.…”

“…While carbon is expected to be insoluble in liquid gallium, previous studies have suggested otherwise and due to the large difference in the surface energies, liquid gallium does not wet amorphous carbon and forms droplets with wetting angles exceeding 120 . 19,[21][22][23] In this letter, we present in situ transmission electron microscopy (TEM) studies of the decay behavior of Ga droplets on amorphous carbon thin films during annealing. From the time-lapsed TEM images, we find that smaller droplets shrink and the volume decay rates depend on the local environment, characteristic of surface-diffusion-limited Ostwald ripening.…”

“…12 More recently, liquid metals are found to be promising for applications in plasmonics, 13,14 as liquid-metal electrodes in batteries, 15 as ultra-stretchable conductive wires, 16 and as catalysts for the growth of nanowires 17,18 and graphene. 19,20 For any of these applications, thermochemical stability of liquidmetal/solid interfaces is important since it affects properties such as wettability, adhesion, chemical reactivity, reflectivity, thermal and electrical conductivities, optoelectronic properties, and the size of the liquid droplets. Here, we focus on understanding the thermal stability of liquid-gallium/amorphous-carbon interfaces.…”