Effect of electrical discharge power on mechanical properties of N-DLC films deposited by atmospheric DBD plasma

Abstract

Abstract At atmospheric pressure, dielectric barrier discharge of a mixture of nitrogen gas and n-hexane solution has been used to deposit N-DLC films on Pyrex glasses. The composition and the structure of the deposited films have been studied by FTIR and Raman spectra. The surface morphology of films is performed by analyses of FESEM, EDX, and AFM. According to the results of Raman spectra, the ID/IG ratio has been decreased, FWHM of G peak has been increased and the G peak position has been moved to lower wavenumbers. Based on obtained results, increasing electrical discharge power leads to increasing sp3 content and structural transition from the graphitized to amorphous structures. The sp3 content is related to C–H, C–C, and C–N bonds. With the more formation of C–C and C–N bonds than C–H bonds, mechanical properties of hardness and scratchability are strengthen while more increment of C–H bonds in the deposited films compared to two other bonds leads to decrease these properties. Discharge power increment leads to the changing of the adhesion strength as another the mechanical property due to the variation of the hydrogen content, the surface bonding rate, and penetration of the species to the substrate.