Controlling graphene structures and electronic properties by Ion beam irradiation*

Irradiation of ion into graphene is interesting in view of defect-introduction and chemical modification. In this study, we attempted 200 keV Au or I ion injection to graphene. Irradiation to bear graphene will cause damage, so a sacrificial layer protecting graphene was designed and fabricated on the surface. NaCl thin-film was applied for sacrificial layer, where it has been confirmed NaCl hardly affects structural and electronic properties of graphene after removal process. Raman spectroscopy of Au or I ion irradiated graphene by using NaCl thin-film as a sacrificial layer, shows peculiar G band intensity of graphene near 1580 cm-1, indicating honeycomb structure of graphene was preserved after irradiation . Also defects that cause significant intervalley scattering (D band : 1340 cm-1) and intravalley scattering (D’ band : 1620 cm-1) appeared after irradiation. Field effect transistor (FET) of graphene was fabricated after irradiation, and the mobility of irradiated graphene was measured by applying gate voltage sweep range. The mobility of Au and I irradiated graphene decreased down to 0.114 cm2 / Vs and 0.034 cm2 / Vs respectively, being responsible for extremely less conductivity.