Effects of X-ray irradiation on the structure and field electron emission properties of vertically aligned few-layer graphene

Vertically aligned few-layer graphene is prepared using microwave plasma enhanced chemical vapor deposition. The vertically aligned few-layer graphene is irradiated by X-ray of different doses from synchrotron radiation. The main structure of vertically aligned few-layer graphene is found to remain unchanged after X-ray irradiation both in high and low vacuum. X-ray photoelectron spectroscopy results reveal that the oxygen content in pristine and irradiated few-layer graphene remain unchanged after X-ray irradiation in high vacuum. When irradiated in low vacuum, the oxygen content in few-layer graphene increases with X-ray dose. For the vertically aligned few-layer graphene irradiated in low vacuum, the work function first increases and then slightly decreases with further increase irradiation dose from 9.0 × 1014 to 3.6 × 1015 phs/cm2. The field electron emission turn-on field is observed to increase from 4.0 to 9.1 MV/m after X-ray irradiation with the dose of 3.6 × 1015 phs/cm2. The mechanism of the changes in work function and field emission performance of vertically aligned few-layer graphene after X-ray irradiation in low vacuum are discussed.