We report that single-layer graphene on a SiO_2/Si substrate withstands ion bombardment up to ~7
times longer than expected when exposed to focused Ga^+ ion beam. The exposure is performed in
a dual beam scanning electron microscope/focused ion beam system at 30 kV accelerating voltage
and 41 pA current. Ga^+ ion flux is determined by sputtering a known volume of hydrogenated
amorphous carbon film deposited via plasma-enhanced chemical vapor deposition
