Development of high sensitivity graphene gas sensor through ion beam irradiation

Graphene has been intensively studied due to its 2D properties and the functionality of gas sensors. The electrical properties of graphene can be affected by the adsorption of gas and, thus, measurements of resistance can detect the existence of gas on the graphene surface. When defects are introduced in the graphene, the adsorption energy between graphene and gas is increased and the sensitivity is enhanced. Defects can be introduced by ion beam irradiation, and the sensitivity can be measured by the resistance changes. This research revealed that the sensitivity of the defected graphene is enhanced about 15 times larger than prestine graphene by CO flow. For NH3 and NO2 gas, the sensitivity is also enhanced compared to the pristine graphene, which is expected by theory. On the other hands, the physical property changes by ion beam irradiation are also investigated. Defect is a function of dose, energy, and ion species. For example, the amount of defect increases with increasing dose and ion species. However, the energy dependence is somewhat complicated. While the amount of defect increases with increasing energy for Kr ion up to 60 keV, the amount of defect decreases with increasing energy for N or H. By introducing LET (Linear Energy Transfer), we can create an universal law which can explain the relation between defects and all the parameter of ion beam irradiation.