UC Berkeley

Despite numerous investigations of amorphous carbon (a-C) films, a comprehensive study of the feasibility and optimization of sub-5-nm-thick a-C films deposited onto the write pole of heat-assisted magnetic recording (HAMR) heads is lacking. The main objective of this study was to identify the role of pulse substrate bias voltage and C⁺ ion incidence angle on the structure and thickness of 1-4-nm-thick a-C films deposited by a rather new thin-film deposition method, known as filtered cathodic vacuum arc (FCVA). The cross-sectional structure of a-C films synthesized under various FCVA conditions was examined by high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). It was found that film growth under process conditions of low-to-intermediate substrate bias voltage (in the range of -25 to -100  V), low ion incidence angle (10°), very short deposition time (6 s), and fixed other deposition parameters (65% duty cycle of substrate pulse biasing and 1.48 × 10¹⁹ ions/m²·s ion flux) yields a-C films of thickness ≤4 nm characterized by a significant content (~50-60 at%) of tetrahedral (sp³) carbon atom hybridization. A threshold where sp³ hybridization is greatly reduced due to limited film growth was determined from the HRTEM/STEM and EELS measurements. The results of this study demonstrate the viability of FCVA to produce extremely thin and uniform protective a-C films with relatively high sp³ contents for HAMR heads.