The Role of Duty Cycle of Substrate Pulse Biasing in Filtered Cathodic Vacuum Arc Deposition of Amorphous Carbon Films

The effect of the duty cycle of substrate pulse biasing on the structure (hybridization), thickness, residual stress, and roughness of amorphous carbon (a-C) films deposited by filtered cathodic vacuum arc was examined in the light of high-resolution transmission electron microscopy, cross-sectional electron energy loss spectroscopy, Raman spectroscopy, residual stress, and atomic force microscopy measurements. The film structure and composition reveal a multilayer architecture consisting of an interface layer of C, Si, and (possibly) SiC, a buffer layer with varying sp³ fraction and relatively constant carbon concentration, a bulk layer with constant and high sp³ concentration, and a surface layer rich in sp² hybridization. It is shown that a 65% duty cycle yields the smoothest and thinnest a-C films with relatively high sp³ content, whereas a 75% duty cycle produces relatively thicker and rougher a-C films with maximum sp³ carbon concentration and highest residual (compressive) stress. The results of this study have direct implications in high-density magnetic recording, where smooth, ultrathin a-C films with high sp³ content are of critical importance to the longevity and reliability of hard-disk drives.