Degradation of Carbon Overcoat Subjected to Laser Heating in an Inert Gas Environment in Thermally Assisted Magnetic Recording

Because the diamond-like carbon (DLC) thin film overcoat on a hard disk surface plays an important role in maintaining the reliability and durability of the head-disk interface, DLC degradation is a critical issue in thermally assisted magnetic recording (TAMR). The use of helium in hard disk drives (HDDs) is being developed to decrease air-induced structural vibrations, windage loss, and temperature rise. TAMR technology is suggested to be put to practical use in a helium environment in HDDs. In this paper, fundamental experiments have been conducted to understand the structural stability or degradation of an ultrathin DLC overcoat subjected to laser heating in an inert gas environment. An inert gas environment was simulated using nitrogen gas. The degradation of DLC thin films fabricated through chemical vapor deposition was investigated by varying the laser irradiation duration and controlling the intensity of the laser, and it was evaluated through Raman spectroscopy. The differences in the damage mechanisms between an inert gas and air environments were elucidated. We found that the degradation of DLC thin films by oxidation would be significantly less in an inert gas environment than in an air environment.