Modification of Graphene on a Copper Grid during Femtosecond Laser Irradiation: Electron Diffraction and Raman Spectroscopy Studies.

The modification of a graphene sheet, which was fabricated by chemical vapor deposition on a close-meshed copper grid, during powerful femtosecond laser irradiation is studied. The process of long-term irradiation of a sample in vacuum is found to be accompanied by (1) breaking carbon bonds, which is indicated by a decrease in the intensities of the reflections corresponding to electron-beam diffraction by graphene and (2) the formation of new products, which is indicated by the appearance of new diffraction rings and a change in the Raman spectrum of the sample. The compositions of the forming chemical compounds are analyzed. Copper oxides Cu2O and CuO are shown to form predominantly on the sample surface as a result of the chemical reactions induced by powerful femtosecond laser pulses. [ABSTRACT FROM AUTHOR]