Depletion of monolayer liquid lubricant films induced by high-frequency pulsed-laser heating in thermally assisted magnetic recording

In this study, lubricant depletion due to high-frequency pulsed-laser heating was investigated for lubricant films with thicknesses of both more than and less than one monolayer. A conventional lubricant, Zdol2000, was used. It was found that the critical temperature at which the lubricant begins to deplete owing to laser heating was strongly dependent on the lubricant film thickness. In the case in which the thickness of the lubricant film was less than one monolayer, this temperature was approximately 170 °C higher than it was when the thickness was more than one monolayer. To analyze the lubricant depletion mechanism, we examined the tested lubricant film using temperature programmed desorption (TPD) spectroscopy. It was found that the lubricant depletion characteristics due to laser heating could be explained using the experimental TPD results for the tested lubricant film, and that the depletion mechanism involves the desorption or decomposition of the lubricant molecules, which interact with the diamond-like carbon thin films when the lubricant film thickness is less than one monolayer. Further, the results of TPD and of a thermogravimetric analysis (TGA) of the lubricant were compared. The thermal robustness of the ultra-thin liquid lubricant films was found to be greater than that of the bulk lubricant materials.