Near room-temperature synthesis of transfer-free graphene films

Abstract

Large-area graphene films are best synthesized via chemical vapour and/or solid deposition methods at elevated temperatures (~1,000 °C) on polycrystalline metal surfaces and later transferred onto other substrates for device applications. Here we report a new method for the synthesis of graphene films directly on sio 2 /si substrates, even plastics and glass at close to room temperature (25-160 °C). In contrast to other approaches, where graphene is deposited on top of a metal substrate, our method invokes diffusion of carbon through a diffusion couple made up of carbon-nickel/substrate to form graphene underneath the nickel film at the nickelsubstrate interface. The resulting graphene layers exhibit tunable structural and optoelectronic properties by nickel grain boundary engineering and show micrometre-sized grains on sio 2 surfaces and nanometre-sized grains on plastic and glass surfaces. The ability to synthesize graphene directly on non-conducting substrates at low temperatures opens up new possibilities for the fabrication of multiple nanoelectronic devices.

Progress and Challenges in Transfer of Large‐Area Graphene Films

“…It is necessary to optimize the methods to product LAG films with high quality. In recent years, the transfer‐free growth methods where graphene grew directly on target substrates have been reported 88, 89, 90, 91. Graphene grown by the “transfer‐free” method can be directly used without further transfer.…”

Monolithic graphene oxide sheets with controllable composition

“…The large graphitic area in the GO surface supports our hypothesis that the parent GO consists of a honeycomb lattice that is decorated with oxygenated functionalities. Bi-and multi-layer (r4 layers) regions, which could be attributed to the ridge structures 14 , were frequently detected by HR-TEM. Both regions displayed distinct Moiré patterns that were caused by the stacking of individual hexagonal graphitic layers with different orientations 32 .…”

“…These spectra indicate the significant presence of foreign species in the graphene framework. The spectra for all of the samples exhibit three primary features: a D band at B1,348 cm À 1 , a G band at B1,592 cm À 1 and a 2D band at B2,687 cm À 1 , which are all typical peak positions for graphene 14,[16][17][18][19][20][21] . However, the Raman spectra of the samples consistently show an intense D band (I D /I G Z1.0) related to domain boundaries, impurities and growth-nucleation sites [22][23][24][25] .…”

“…1i, illustrate the uniformity of the samples over a large area (70 mm  70 mm). The samples primarily consisted of a singlelayer graphene framework (as identified by I G /I 2D r0.4 and a FWHM of the 2D band of B38 cm À 1 ) and bi-and multi-layered regions that resembled ridge structures 14 akin to GBs in the annealed Cu foils. The graphene framework seems to be predominantly composed of a single layer when analysed using Raman spectra and maps.…”

“…We developed a solution-free, physical synthesis process for the synthesis of monolithic chemically modified C sheets on Cu surfaces that relies on a diffusionassisted synthesis (DAS) approach 14 , as shown in Figure 1a. Initially, 1-mm-thick polycrystalline Cu foils were used; these Cu foils exhibited strong rolling features with irregular grain structures that were produced during the manufacturing process 15 ( Supplementary Fig.…”