Control of the ultrafast photo-electronic dynamics of a chemical-vapor-deposited-grown graphene by ozone oxidation

Abstract

Diverse ultrafast dynamics have been reported on different graphene prepared by different methods. Chemical-vapor-deposited (CVD) growth is regarded as a very promising method for highly efficient production of graphene. However, CVD-grown graphene usually presents only one of the diverse ultrafast dynamics. Thus, control of the ultrafast photo-electronic dynamics of CVD-grown graphene is vital to present diversity for different photodetection applications of CVD-grown graphene. In this paper, we report on the first realization to our knowledge of control of the ultrafast dynamics of CVD-grown graphene and the manifestation of diverse ultrafast dynamics on sole CVD-grown graphene. We study the ultrafast photoelectronic dynamics of CVD-grown graphene with different degrees of oxidation caused by ozone oxidation using femtosecond time-resolved transient differential transmission spectroscopy, and we find that the ultrafast dynamics can evolve obviously with the time of ozone oxidation. The diverse ultrafast dynamics reported previously on different monolayer graphenes prepared by different methods are achieved on the sole CVD-grown graphene by controlling oxidation time. The mechanism for manipulation of the ultrafast dynamics by ozone oxidation is revealed by Raman spectroscopy as the control of the Fermi level of CVD-grown graphene. Simulations of dynamics based on the optical conductivity model of graphene and Fermi level change well reproduce the observed diverse ultrafast dynamics. Our results are very important for the diverse applications of graphene and open a new path toward the diverse ultrafast dynamics on sole graphene prepared by any method.