Calcium doped diamond-like carbon films fabricated by plasma immersion ion implantation

Diamond like Carbon (DLC) films have been computationally used as protective coatings for many purposes and doping of DLC films has been shown to enhance certain tribological properties. However, doping is a relatively novel approach with respect to the modification of the surface biomedical properties of DLC films. In the work reported here, we implanted a biological friendly element, calcium, into DLC using plasma immersion ion implantation (PHI) to enhance its surface biocompatibility. Calcium is also an important element in bones and calcium-doped DLC may be potentially useful in orthopedic applications. Acetylene gas (C₂H₂) was initially used to synthesize the hydrogenated amorphous carbon films by PIII, and subsequent calcium implantation was conducted in the same machine. Calcium has a high boiling point (1484°C at 1 atmospheric pressure) and is chemically reactive in air. Therefore, in our work, we designed a special ion source. The Ca powder was evaporated utilizing electron bombardment and the calcium plasma was produced by pulsed high-voltage glow discharge. The film properties were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). With regard to the hemo-compatibility, platelet adhesive tests were performed. The Caimplanted DLC films exhibit enhanced biomedical properties and the details will be discussed in this paper.