Surface properties of ultra-thin tetrahedral amorphous carbon films for magnetic storage technology

Diamond-like carbon (DLC) films form a critical protective layer on magnetic hard disks and their reading heads. Film thickness below 2 nm and roughness well below 1 nm are needed for storage density of 200 Gbityinch . We use atomic force 2 microscopy to study the roughness evolution vs. thickness of highly sp hydrogen-free tetrahedral amorphous carbon (ta-C). The 3 roughness of films r generally follows fractal scaling laws, increasing with film thickness h as rsah , where b is the growth b exponent. For a fixed film thickness and scan length l, the roughness varies as l , where a is the roughness exponent. We find a a;0.39 and b;0–0.1. We performed Monte Carlo simulations, modelling the smoothing effects caused by the thermal spike. The simulation results closely match the experimental findings and define a new growth mechanism for ta-C films. The structural evolution of these ultra-thin films is monitored by Raman spectroscopy. A linear relation between G-peak dispersion and Young’s modulus is found. The 2-nm-thick ta-C films are pin-hole free, corrosion resistant, have a Young’s Modulus of ;100 GPa, sp content of ;50% and roughness of ;0.12 nm. So, data storage density of 1 Tbityinch could be achieved. 2 2003 Elsevier B.V. All rights reserved.