Space-charge limited and ultrafast dynamics in graphene-based nano-gaps

We show that nano-gaps formed in graphene by utilizing a focused helium ion beam can act as ultrafast photoswitches. By temperature-dependent, time-integrated, and ultrafast photocurrent measurements, we demonstrate that the optoelectronic dynamics across such nano-gaps are dominated by a space-charge limited current in combination with the ultrafast dynamics of hot electrons. The demonstrated methodology allows the creation of ultrafast photoswitches with an amplification gain exceeding the ones as formed by pristine graphene.