Nitrogenated carbon layer on magnetic recording disks

Abstract

Abstract Hydrogenated carbon films have been used in the magnetic recording industry as a protective overcoat for memory disks for many years. In recent years, with shortening of the gap between the head and the disk (as in proximity heads), the inclusion of nitrogen in the films to form hydro/nitrogenated films has also aroused tremendous interest. In this study, nitrogenated amorphous carbon films (without hydrogen) (a-C:N) of thickness ranging from 5 to 20 nm were deposited on rigid magnetic disks via the magnetron sputtering of a graphite target. The deposition was conducted in an argon/nitrogen atmosphere under RF (radio frequency) substrate bias power. A scanning probe microscope (SPM) with a contact mode of atomic force microscopy (AFM) mode was used in the roughness determination. A Raman spectroscope was employed to study the structural evolution of the coatings with varying nitrogen/argon proportion and flow rate, radio frequency substrate bias and target power density. The surface contact angle between the a-C:N coating and deionized water was measured using a Rame–Hart goinometer. Under the deposition conditions, the carbon thickness decreased with gas flow rate, but increases with nitrogen content. An increase in contact angle with bias power and decrease with flow rate were also observed. The roughness (Ra) of the coatings did not change because the coating was too thin to change the original substrate roughness. Also studied were the Raman peak positions, and the D-band and G-band intensity ratio and their relationship with the processing parameters.