Photoresponse in graphene field effect transistor under ultra-short pulsed laser irradiation

摘要

We have developed the ultra-short pulsed laser processing methods for patterning of graphene field effect transistors in topological and chemical way. We investigated in details the photoresponse in graphene FETs before and after laser- induced modification for laser fluence below threshold energy. We observed two different mechanisms of the photoresponse under ultra-short laser pulses (280 fs). The photocurrent, observed for both pristine and laser processed graphene is raised because the laser induced charge is transferred from graphene to trapped levels in SiO_2 surface resulting in electrostatic Dirac point shift. For laser oxidized areas we observed more pronounced photocurrent because of heterojunction formation in laser-processed area. While for electrostatic effect the relaxation time estimated as 50 seconds, the heterojunction relaxation was observed for less than 3 ms.