Pulsed UV-laser-induced chemistry of perfluoropolyether lubricant film

Abstract.

We investigate the molecular structure change of laser-irradiated perfluoropolyether lubricant on disk media by using mass spectroscopy. A KrF excimer laser with a wavelength of 248 nm was used to irradiate the lubricant film (2 nm) on a carbon overcoat surface. We found that two unique mass peaks emerged from the laser-irradiated lubricant mass spectra, which are attributed to OH-CHF-O(:H⁺)-CHF-OH and F-COO-CF₂-CF₂-CF₂-CF₂ ⁺ respectively. When thelaser fluence increases to 100 mJ/cm², these two unique mass peaks start to be enhanced drastically while the abundance of the end group of the lubricant, CF₂CH₂OH, remains almost constant, indicating that the two unique species are generated from the scission and re-arrangement of the backbone ether chains. With a laser fluence beyond 140 mJ/cm², the disk media surface damage is observable and lubricant evaporation is the main pathway.