Versatile Polymer-Free Graphene Transfer Method and Applications

Abstract

A new method for transferring chemical vapor deposition (CVD)-grown monolayer graphene, to a variety of substrates is described. The method makes use of an organic/aqueous biphasic configuration, avoiding the use of any polymeric materials that can cause severe contamination problems. The graphene-coated copper foil sample (on which graphene was grown) sits at the interface between hexane and an aqueous etching solution of ammonium persulfate to remove the copper. With the aid of an Si/SiO2 substrate, the graphene layer is then transferred to a second hexane/water interface, to remove etching products. From this new location, CVD graphene is readily transferred to arbitrary substrates, including three dimensional architectures as represented by atomic force microscopy (AFM) tips and transmission electron microscopy (TEM) grids. Graphene produces a conformal layer on AFM tips, to the very end, allowing the easy production of tips for conductive AFM imaging. Graphene transferred to copper TEM grids provides large area, highly electrontransparent substrates for TEM imaging. These substrates can also be used as working electrodes for electrochemistry and high resolution wetting studies. By using scanning electrochemical cell microscopy, it is possible to make electrochemical and wetting measurements at either a free-standing graphene film or a copper-supported graphene area, and readily determine any differences in behavior.3

Large graphene-induced shift of surface-plasmon resonances of gold films: Effective-medium theory for atomically thin materials

“…A floating graphene on DI water was scooped by Au/glass substrate and could be transferred to any substrates in principle. This method is simpler than many reported polymer-free or support-free methods [46][47][48][49][50][51]. High-quality monolayer graphene was confirmed by Raman ( Fig.…”

Hybrid cold and hot-wall reaction chamber for the rapid synthesis of uniform graphene

“…The greatest difference between the counterpart chambers is that uniform radiation in a HWC provides a large (compared to the size of the specimen) heating zone with a uniform temperature whereas there is a huge thermal gradient between the hot stage (~1000 °C) and the cold walls (~few tens of °C) during the operation of the CWC (bottom inset Figure 1 Figure 2 characterizes graphene grown in a CWC. For this growth, we adopted a recipe similar to what has been developed earlier [1,2,5] and includes: i) heating the copper foil to 1035 °C, ii) annealing for 10 minutes and iii) growth for 10 minutes (CH4 to H2 ratio of 7:2, gas purity grade 6.0, chamber pressure of few mbar). The synthesized graphene covers the surface of the copper thoroughly, yet it suffers from several imperfections (summarized in Table 1):…”

Molecular Caging of Graphene with Cyclohexane: Transfer and Electrical Transport

“…14 The PMMA polymer (i.e., poly(methyl methacrylate)) protects and conforms the surface of graphene and therefore allows transferring large and continuous areas of graphene (Figure 2b). Polymer residuals, however, are inevitable, contaminating the surface of the graphene.…”

“…For the contact stamping method, a wafer was directly placed on graphene floating on the etchant, transferred, and rinsed with water; alternatively, the etchant is replaced by pure water prior stamping. For the hexane-assisted transfer method, we reproduced the protocol from ref (14) by placing a wafer beneath graphene (in the etchant) and fishing from below the graphene with hexane as the top phase. In all four transfer methods, we used a 0.5 M solution of (NH 4 ) 2 S 2 O 8 as a copper etchant.…”

“…12,13 Very recently, a biphasic system composed of an aqueous solution of ammonium persulfate and hexane has been employed for clean graphene transfer. 14 Polymer-free transfers, however, are widely known to induce cracks as graphene is a macroscopic sheet that has to be mechanically maintained while and after the underlying growth catalyst is etched. Polymers are known to protect graphene from cracking and folding at the cost of extensive contamination, highlighting the need for a top phase that can be solidified without the use of polymerization reactions.…”