The researchers in the Material Research Center at Institute of Modern Physics (IMP), Chinese Academy of Sciences, have investigated the irradiation effects of graphene induced by Swift Heavy Ions (SHI) and Highly Charged Ions (HCI). The theoretical reasons for the various irradiation effects of HOPG and graphene are inferred for the first time.
Graphene, which is well known as the thinnest material in the world, has a number of fascinating properties. Its thermal conductivity is 3 times of pure diamond at room temperature. Its storage ability of lithium ions is nearly 10 times of graphite. The electrons speed in graphene reached 1/300 of the light speed, which is 100 times larger than that in silicon. Graphene has opened huge possibilities in electronic device fabrication and has also shown much promise in replacing silicon-based electronics. The investigation of irradiation effects of graphene induced by energetic ions could not only lay a foundation for the application of graphene in a new generation of semiconductor devices, but also regulate the graphene properties on the atomic scale and broaden the application of the two-dimensional material.
Both of SHI (479 MeV 86Kr and 250 MeV 112Sn) and HCI (4 MeV 86Kr19+) were used to irradiate monolayer graphene and highly oriented pyrolytic graphite (HOPG). SHI were provided by the accelerator HIRFL of IMP and HCI were offered by the 320 kV platform for multi-discipline research at IMP. The different irradiation results of graphene and HOPG caused by SHI and HCI were discussed, which indicates the irradiation damage should be considered in the application of graphene. The Lucchese’s phenomenological model was improved to give full line fitting of the experiment data of graphene and HOPG (as shown in figure 1). According to the improved phenomenological model, the energetic ions may cause both structurally disordered and activated regions in graphene. The competing mechanism of these two regions results in three different regions of ID/IG for graphene. In HOPG, however, activated region induced by energetic ions, only two regions of ID/IG variation were detected, which explains the lack of a turning point in the ID/IG behavior.
The work has been published in Carbon 100 (2016) 16-26 (Impact factor 6.075).
The article can be linked as follows:
This work was supported by National Science Foundation of China
Fig. 1 – (a) Comparison of the ID/IG values obtained from Kr19+ irradiated HOPG (square data points) and graphene (circle data points). The fitting line of graphene is and HOPG is given by the improved phenomenological model. (b) The evolution of ID/IG in log-log plot.（Image by IMP）