Soft X-ray irradiation effect on the fluorinated DLC film

•The irradiation effect of the soft X-rays on fluorinated diamond-like carbon film was investigated.•Various film properties and surface properties were found to be changed by the SR irradiation.•Changes in film properties and film thickness did not proceed after the 300 mA h SR exposure.•The stop of change in film properties was ascribable to the decrease of fluorine content in the F-DLC film.

The irradiation effect on fluorinated diamond-like carbon (F-DLC) film was investigated by measuring the dose dependence of various film properties using synchrotron radiation (SR) in the soft X-rays in the SR dose region from 0 to 2000 mA h. Film flatness was maintained but various film properties and surface properties were found to be changed by the SR irradiation. Wettability of the F-DLC film surface increased dramatically within 20 mA h SR exposure, which was ascribed to the decrease in fluorine on the film surface. Film thickness, film density, composition ratio of fluorine atom in film decreased and sp2 / (sp2 + sp3) ratio of carbon atoms increased within 300 mA h SR exposure, which were ascribed to the desorption of species containing fluorine atoms. In addition, dominant desorbed species emitted from F-DLC film were found in the fluorocarbon group, CFx. Changes in film properties and film thickness did not proceed, when fluorine content in the F-DLC film decreased to about 10% after the 300 mA h SR exposure.