Raman spectroscopy measurements of DC-magnetron sputtered carbon nitride (a-C:N) thin films for magnetic hard disk coatings

Abstract

Abstract As a protective coating for hard disks in magnetic storage applications, amorphous carbon nitride (a-C:N) thin films have proved superior to DLC (diamond-like carbon) a-C:H films in terms of durability, wear-resistance and adhesion properties. In this study, we present Raman spectroscopy investigations of a-C:N films which were produced by DC-magnetron sputtering systems. The layers were deposited with a variable nitrogen content, thickness and substrate temperature. Raman measurements were carried out with two different excitation lasers at wavelengths of 488 and 532 nm. The spectra show that besides the typical carbon D- and G-bands, two other characteristic bands are present at approximately 690 and 1090 cm−1. The meaning and identification of these bands is not clear in the literature. In order to obtain more information, the films were also characterized by various analytical techniques, e.g. time-of-flight secondary ion mass spectrometry (ToF-SIMS), Auger electron spectroscopy (AES), ellipsometry, and n+k optical measurements. The Raman G-band position shows a systematic shift with the varying nitrogen content of the films. A comparison of layer thickness and the total area of D-, G- and 1090 cm−1 bands also shows a significant correlation. The results offer Raman spectroscopy as a possible monitoring tool for carbon nitride coatings in the production of magnetic hard disk drives.