01 June 2018 Graphene and flexible substrates

Schematic of how graphene is transferred to glass and PET using PI as an intermediate layer

An international team of researchers reports on a new dry-transfer technique for the fabrication of transparent flexible substrates using graphene. Graphene is a unique 2D material that has shown to have amazing properties which include high intrinsic carrier mobility, tunable band gap, high mechanical strength and elasticity, and superior thermal conductivity, among others. Such unique characteristics make graphene a potential material for many applications, for example its implementation for high-speed transistors, energy/thermal management and chemical/biological sensors.

In order to fully exploit the properties of this material, previous studies have been devoted to understanding how it can be transferable to a wide variety of substrates. Several methods have been developed toward this goal and the most commonly used method is a polymer-assisted transfer process called ‘wet-transfer’. Now, the drawback of this process is that it leaves residues on the substrate, which depose a significant challenge to the fabrication process since it affects the graphene’s electrical and mechanical properties.

In a recent study published in 2D Materials, ICFO researchers Miriam Marchena, Manuel Fernandez, Tong Lai Chen, led by ICREA Prof. at ICFO Valerio Pruneri, in collaboration with researchers led by Dr. Prantik Mazumder and Dr. Robert Lee from Corning Research and Development Corporation, have demonstrated for the first time the direct transfer of graphene from Cu foil to rigid and flexible substrates, such as glass and PET, using as an intermediate layer of thin film of polyimide (PI) mixed with an aminosilane, a process that leaves the substrate free of residues.

With this technique, the team of scientists has obtained as a result a transparent device, thermally stable (350 °C) and free of polymer residue on the device side of the graphene. Their technique is the first step towards making a substrate ready for device fabrication.

The results of the study open a new window toward the use of graphene in the development of devices that can be made smaller and faster when compared to the actual silicon based devices that are beginning to show capability limitations.