Mechanical Properties and Atomic Structure of Diamond-Like-Carbon Films Fabricated by Unbalanced Magnetron Sputtering

概要

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Relationship between mechanical properties of DLC film prepared by UBM method and bonding structure of carbon atoms in film has been revealed by Raman spectrum analysis. Four types of DLC films with different hydrogen content were prepared by UBM method. Increase in hydrogen content in DLC film results in deterioration of hardness. Increase of hardness seems to result in shift of G-peak position toward shorter wavelengths in Raman spectra. Increase in hydrogen content in DLC film leads to deterioration of friction coefficient, but correlation between G-peak position and friction coefficient was not as high as correlation between G-peak position and hardness. So friction coefficient has no stronger relationship with bonding structure than does hardness. In order to clear mechanism of appearance of low friction coefficient of DLC film, changes in sp2 and sp3 bonding components are analyzed using AES-EELFS spectra measured before and after applying sliding friction. Decrease in amount of sp2 bonding component or disordering of sp2 bond has been confirmed. Content of sp2 bond component in film decreases mainly through migration of graphite component to counter material, so that graphite contents in DLC film and counter material reach equilibrium. This is considered to be one of factors of appearance of low frictional coefficient.