Modification of graphene properties by optical forging

Abstract

Graphene is one atom layer thin carbon material that has gained plenty of attention due to its numerous excellent properties. In this thesis a novel method to modify the structure and properties of graphene, called optical forging, is presented. In this method graphene is irradiated using femtosecond pulsed laser light and as a result of it graphene forms three-dimensional structures. Detailed characterizations have revealed that the process of optical forging causes defects to the graphene lattice, which in turn causes lattice expansion and bulging of graphene into the 3D shapes. In addition to this, some amorphous carbon is deposited onto graphene as a side effect, and the formation of the entire 3D shape is a combination of both bulging and deposition. Using nanoindentation measurements, optically forged graphene was determined to have high bending stiffness, which is very different from pristine graphene, which is very flexible. Optically forged patterns are also and more reflective than pristine graphene and they exhibit photoluminescence. As for applications, optical forging can be used to make ultralight scaffold structures from graphene, and potentially to increase the resonance frequencies of graphene resonator devices.