Mai Takashima

Characteristics of Diamond-Like Carbon Films Deposited on Polymer Dental Materials

Characterizations of diamond-like carbon (DLC) deposited on a polymer artificial tooth were performed. DLC films were deposited on dental parts made of poly(methyl methacrylate) (PMMA) resin by dc-pulse plasma chemical vapor deposition (CVD) from methane. Wear resistance test results revealed that a DLC-coated resin tooth has a very high wear resistance against tooth brushing, and endures 24 h brushing without a marked weight decrease. Cell cultivation test results show that DLC plays an important role in preventing cell death. Moreover, a biocompatibility test using a rabbit revealed that a connective tissue in the vicinity of DLC-coated PMMA is significantly thinner than that of noncoated PMMA. The numbers of inflammatory cells in the vicinity of DLC-coated and noncoated surfaces are 0 and 508 cells/mm2, respectively. These results led us to conclude that DLC films are an excellent material for use as the coating of a polymer artificial tooth in terms of not only high wear resistance but also biocompatibility.

Synthesis of Antimony Doped Amorphous Carbon Films

We report the effects of antimony (Sb) doping on the electrical and optical properties of amorphous carbon (a-C:H) films grown on silicon and copper substrates by magnetron sputtering deposition. For film deposition, the mixture targets fabricated from carbon and antimony powders was used. The atomic concentration of carbon, hydrogen, and antimony, in the film deposited from the 1.0 mol% Sb containing target were 81, 17, 2 at.%, respectively. These elements were homogeneously distributed in the film. On the structural effect, the average continuous sp2 carbon bonding networks decreased with Sb concentration increasing, and defects in the films were increased with the Sb incorporation because atomic radius of Sb atoms is twice larger size than that of carbon. The optical gap and the electrical resistivity were carried out before and after the Sb doping. The results show that optical gap dropped from 3.15 to 3.04 eV corresponding to non-doping to Sb-doping conditions, respectively. The electrical resistivity reduced from 10.5 to 1.0 MΩm by the Sb doping. These results suggest the doping level was newly formed in the forbidden band.

Detecting Method of Bulk Defects in DLC Films Using Light Scattering

Diamond-like carbon (DLC) film has various micro-size defects like pinhole, void and particle. When DLC film is exposed to white light, light is scattered in all direction at defects in DLC film. In this paper, defects in DLC film are detected by observing scattering light from defects under dark-field microscope. DLC film has wavelength dependence of transmittance. Therefore, using its wavelength dependence allows to separate surface and inside defects of DLC film. This paper describes development of bulk defects detecting system using optical filtering and scattering light detecting. Bulk defects of DLC films were successfully separated into surface defects and inside defects. This detecting method of defect is nondestructive and easy, and applicable to DLC films as well as other coating films.