Research About Effects Of Low Temperature Oxygen Plasma Treatment On Fracture Toughness And Adhesion Characteristics Of Monolayer Graphene

Graphene is a two-dimensional, zero bandgap material completely composed of carbon atoms, which has large development space in the field of super capacitor, flexible display, corrosion protection materials and thermal materials due to its unique properties, such as excellent mechanical properties, high specific surface area and ultra-high electron mobility. Since the discovery of graphene, there are many studies on the modification of graphene using low-temperature oxygen plasma, but few studies on the adhesion and fracture toughness that can not be ignored in the graphene based devices. In this paper, the properties, applications and preparation methods are presented. And the adhesion and fracture toughness of monolayer graphene are discussed through optical microscope, XPS, Raman and AFM.Monolayer graphene was prepared by chemical vapor deposition, and then transferred to the 90 nm SiO2/Si substrate. Raman, XPS and AFM are utilized to characterize the changes before and after treatment. The XPS spectra indicates that there are many C-OH and C=O functional groups introduced into graphene. The D and D' peak appear in Raman spectra of graphene. The two peaks' intensity and ID/IG increase after treatment. Meanwhile, right shift was found in the G peak and left shift in the 2D peak with the increase of exposure time. According to the Raman spectra, n-doped and defects are introduced into the graphene during the treatment. The increase of defect density and the refinement of grain crystal was found with the increase of exposure time. Furthemore, the tensile strain introduced by the treatment becomes larger with the increase of exposure time. These studies on the microstructure of graphene before and after low-temperature oxygen plasma treatment will provide a theoretical support for the results of the following experiments.In the AFM images, with the increase of exposure time, the surface roughness and adhesion of graphene become larger as well as the variation of C-OH. Meanwhile, the fracture toughness of graphene becomes smaller. The samples was changed from the character of water-repellent to hydrophilic during the treatment, which is responsible for the variations of roughness and adhesion. Moreover, the stress corrosion from adsorption of water vapor on the graphene and the tensile strain introduced by the treatment cause the decrease of the fracture toughness of graphene. The research results will provide a theoretical basis for the application of graphene treated by low-temperature oxygen plasma.