Fabrication of Graphene-Based Transparent Conducting Thin Films

Abstract

Chemical vapor deposition (CVD)-grown graphene and graphene oxide (GO) have been the main starting materials to produce graphene-based transparent conductors (TCs) [1,2]. For the CVD-grown graphene, the underlying substrates need to be removed so that the graphene sheets can be transferred onto the device substrates. Several strategies have been developed to transfer graphene sheets and they include the etching and stamping method [3,4], thermal release method [5], photoresist method [6], roll-to-roll transfer method [7], and general method [8]. Another lowcost route to produce graphene-based TCs on a large scale is to synthesize GO thin films and then reduce them. The ease of solution process of GO sheets due to their high solubility in aqueous solutions has made it a more viable and favorable approach [2]. Once a GO dispersion is produced, GO films can be formed on a substrate using different deposition techniques, including electrophoretic deposition (EPD), spin coating, spray coating, dip coating, transfer printing, LangmuirBlodgett (L-B) assembly, rod coating, and inkjet coating [1]. CVD-Grown Graphene-Based TCs Etching MethodAfter graphene is grown on a metal substrate as described in Sect. 2.2, graphene needs to be transferred to the device substrate via a post-transfer process, which usually involves two main steps: (i) etching of the metal substrate and (ii) transfer of graphene onto the target substrate. The removal of growth substrate, such as Cu and Ni, is usually performed by immersing the substrate with the graphene film into the etching bath until a free-standing graphene membrane floating on the solution can be readily observed [9][10][11]

Support-Free Transfer of Ultrasmooth Graphene Films Facilitated by Self-Assembled Monolayers for Electronic Devices and Patterns

“…Transferring chemical vapor deposition (CVD)-grown graphene films from metal surfaces to target substrates while preserving their high quality is a major challenge, particularly for use in electronic devices. − Thus far, transfer techniques have been reported involving the use of support materials such as polymers, namely, poly­(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS), poly­(bisphenol A carbonate) (PC), thermal release tape (TRT), and also through “electrochemical delamination”. − The use of pressure sensitive tape has recently been described by Kim et al, who stated that this is an effective method for transfer of graphene from Cu foil and to various substrates . However, the polymer/tape-based methods suffer from support material residues left on the surface of the transferred graphene films, and additional cleaning process­(es) that may lead to cracking or folding/wrinkling of the graphene, resulting in a poorer performance of the graphene-based devices .…”