Addressing the Achilles’ Heels of Amorphous Carbon Overcoats with Doping: Mechanisms of Thermal and Oxidative Degradation

Harsh environments pose materials durability challenges across different sectors. While amorphous carbon materials have been used as coatings in environmentally-demanding applications owing to their unique properties, their limited thermal stability and high reactivity in oxidizing environments have inhibited their use in many technologies. Silicon- and oxygen-containing hydrogenated amorphous carbon (a-C:H:Si:O) films are promising for several applications because of their higher thermal stability and lower residual stress compared to hydrogenated amorphous carbon (a-C:H). However, an understanding of their superior thermo-oxidative stability compared to a-C:H is lacking.
Here, we performed X-ray photoelectron/absorption spectroscopy experiments and molecular dynamics simulations to show how the introduction of silicon and oxygen in a-C:H enhances: 1) the stability at elevated temperatures in both vacuum and oxidizing environments; and 2) the resistance to degradation upon exposure to the harsh conditions of low Earth orbit (LEO) aboard the International Space Station. These findings provide a novel physically-based understanding of the superior stability of a-C:H:Si:O in harsh environments compared to a-C:H.