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[19p-P4-8] Comparison between X-ray irradiation desorption and thermal desorption detachment process of fluorinated DLC films
Keywords:diamond-like carbon film, soft X-rays, thermal desorption spectrum
Fluorinated diamond-like carbon (F-DLC) films are known to exhibit particularly high insulation, a low dielectric constant, a smooth surface, low surface free energy, and chemical inertness, and are used to improve tribological properties and for the corrosion protection of steel and alloys. In addition, F-DLC films are expected to be utilized as a coating material on medical devices, electronic devices, and astronautical parts because of their excellent stain resistance due to their low surface free energy. In the industrial fields employing these applications, tolerance to X-rays is required. In general, DLC films have very strong tolerance to soft X-ray irradiation. However, we have observed that the irradiation of soft X-rays on highly hydrogenated DLC (H-DLC) films and F-DLC films induced the etching and/or modification of the films. In the present study, desorption process of F-DLC films and H-DLC films by the irradiation of soft X-rays was discussed by the comparison with thermal desorption.
H-DLC film and F-DLC film were deposited on Si wafers using an amplitude-modulated radio-frequency plasma-enhanced chemical vapor deposition method. The desired film thickness was 200 nm. Soft X-ray irradiation on H-DLC films and F-DLC films were performed at BL06 in the NewSUBARU synchrotron facility of the University of Hyogo. The SR at the BL06 sample stage had a continuous spectrum from infrared to soft X-rays, below 1 keV. Desorbed species from the H-DLC film and F-DLC film surface by using soft X-ray irradiation were measured using a quadruple mass spectrometer (QMS) (Anelva, Q-M400QA-M). The detectable mass range was from 1 to 400. Thermal desorption spectra of H-DLC films and F-DLC films were measured using hand-made thermal desorption apparatus in the temperature range of 300-1100 K, raising the temperature at a rate of 5 K/min.
In desorption of H-DLC films, dominant desorption species were found to be hydrogen molecules both soft X-ray irradiation and thermal desorption. On the other hand, in desorption of F-DLC film, fluorine and carbon atoms were dominantly desorbed by thermal rise, while fluorinated carbon species were dominantly desorbed by the soft X-ray irradiation. This discrepancy indicated that desorption from F-DLC films by the irradiation of soft X-rays was not same as thermal desorption process, and this result was consistent to that the independence of desorption rate from F-DLC films on the substrate temperature in the irradiation of soft X-rays.
H-DLC film and F-DLC film were deposited on Si wafers using an amplitude-modulated radio-frequency plasma-enhanced chemical vapor deposition method. The desired film thickness was 200 nm. Soft X-ray irradiation on H-DLC films and F-DLC films were performed at BL06 in the NewSUBARU synchrotron facility of the University of Hyogo. The SR at the BL06 sample stage had a continuous spectrum from infrared to soft X-rays, below 1 keV. Desorbed species from the H-DLC film and F-DLC film surface by using soft X-ray irradiation were measured using a quadruple mass spectrometer (QMS) (Anelva, Q-M400QA-M). The detectable mass range was from 1 to 400. Thermal desorption spectra of H-DLC films and F-DLC films were measured using hand-made thermal desorption apparatus in the temperature range of 300-1100 K, raising the temperature at a rate of 5 K/min.
In desorption of H-DLC films, dominant desorption species were found to be hydrogen molecules both soft X-ray irradiation and thermal desorption. On the other hand, in desorption of F-DLC film, fluorine and carbon atoms were dominantly desorbed by thermal rise, while fluorinated carbon species were dominantly desorbed by the soft X-ray irradiation. This discrepancy indicated that desorption from F-DLC films by the irradiation of soft X-rays was not same as thermal desorption process, and this result was consistent to that the independence of desorption rate from F-DLC films on the substrate temperature in the irradiation of soft X-rays.