Mar 27, 2012
Plasma team investigates optimal method of fluorinating graphene
The properties of graphene films are sensitive to local perturbations, such as surface charges and absorbed gas molecules. Recently, plasma-based functionalization has been reported as a gas-phase approach for changing the electronic structure of graphene – for example, by doping and band gap opening. However, most of the studies concentrate on changes to graphene introduced by oxygen or hydrogen plasma. One way to create more stable graphene derivatives with stronger binding between agents and carbon is to use fluorine. To follow this up, researchers in China have systematically investigated the chemical functionalization of graphenes using fluoric plasma treatments (CHF3 and CF4) and identified the most appropriate method.
The G and 2D Raman peaks of n-layer graphenes show upshifts after treatment by these two kinds of plasma, indicating p-doping. Under the same experimental conditions, D, D’ and D+G peaks can clearly be observed for monolayer graphene, whereas these peaks are absent for thicker n-layer graphenes (n≥2), which indicates that the fluorination of monolayer graphene is more feasible than for thicker graphenes.
Comparison of I(2D)/I(G) and I(D)/I(G) of CHF3/CF4 plasma-treated graphenes indicates that CF4 plasma treatment introduces more p-doping and less defects. Meanwhile, the fluorination of monolayer graphenes by CF4 plasma is reversible through thermal annealing whereas the CHF3 plasma treatment is irreversible.
Applications for fluorinated graphene include electronic devices and hybrid materials.
The researchers presented the work in the journal Nanotechnology.
About the author
The study was conducted by a team of researchers from the National Center for Nanoscience and Technology (NCNST) in Beijing, China. The work is supported by the National Science Foundation of China. Prof. Dr Sun is team leader and the group is interested in the synthesis, characterization, electrical and surface properties of carbon nanotubes (CNT) and graphene. Minjiang Chen, a PhD student, performed the plasma-treatment experiments, Raman spectroscopy analysis and scanning electronic microscopy characterization, along with Haiqing Zhou and Caiyu Qiu, a PhD student and a doctor, respectively. Huaichao Yang and Fang Yu are PhD students focusing on the synthesis of graphene and thermal evaporation of metal films on graphene layers.