Stefan Saager, Lars Klose, Bert Scheffel, Matthias Fahland, Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, Dresden, Germany
Graphene has extraordinary properties, such as very high electrical and thermal conductivity, mechanical strength and elasticity. This enables a variety of potential applications as electrical energy storage devices, solar cells, smart windows, OLEDs, displays and membranes. However, the industrial potential can only be exploited and evaluated if there are suitable manufacturing processes. We investigated the growth of graphene on low cost substrate material by plasma-enhanced chemical vapor deposition (PECVD) at different process conditions in an inline roll-to-roll process. A stainless steel strip was coated with a 50-70 nm thick Cu catalyst layer on both sides by a face-to-face arranged magnetron sputtering configuration in a first process step. Secondly, the strip was plasma processed by passing an inverted magnetron arrangement, where the moving substrate serves as the grounded cathode of a magnetron discharge. The Ar plasma discharge heats up the substrate rapidly and by adding methane or acetylene precursor, PECVD of graphene is induced. The processed surface was characterized by Raman spectroscopy. Applying a plasma power density of 7.7 Ws/cm² and a process speed of 20 mm/s to the freshly deposited Cu catalyst, a moderate temperature of 720 °C was reached and led to a polycrystalline graphene growth simultaneously.