Integrated Catalytic Fabrication Approaches for Graphene-Based Electronic Devices
Catalytic Chemical Vapour Deposition (CCVD) of graphene is the most promising production method of large-area, high-quality graphene. However, the required transfer step from the metal growth substrate to the desired dielectric substrate is a major bottleneck for the integrated manufacturing of graphene-based electronic devices.
The performance of a typical graphene field effect transistor (GFET) is marred by the presence of graphene grain boundaries, atmospheric doping and polymer residues from the transfer and fabrication steps. We here show that these three factors all interact with each other. The grain boundaries acts as a preferential adsorption site for polymer residues from the transfer step, which reduce the electronic properties of graphene and help to retain atmospheric doping. These polymer residues become embedded below the Al
The transfer-free catalytic graphene growth, directly at the interface between the metal catalyst and the desired dielectric substrate, is an interesting alternative for the integrated manufacturing process. However, the growth mechanism is poorly understood so far. We here present a detailed study of the feasibility, challenges and mechanism of growing these interface graphene films (IGF). Firstly, we find that with typical metal catalysts -such as nickel or copper-, the commonly used SiO
Based on our findings and developed understanding of the IGF growth mechanism, we propose a novel engineered catalyst structure for high-quality, homogeneous, full coverage and controllable IGF growth, consisting of a Cu/ Ni/aC/dielectric stack. The copper both blocks the carbon from forming graphene at the free metal surface as well as gradually reduces the carbon solubility in the nickel layer. This pushes the dissolved carbon towards the interface and causes isothermally supersaturation and IGF growth to occur. Various challenges and solutions in the form of copper diffusion barriers are discussed to control the kinetics of this system and improve the resulting IGF quality.
This work represents an important milestone for the IGF growth by systematically analysing the fundamental interactions, thermodynamics and kinetics and provides a stepping stone for further research in the area.