Direction dependent etching of diamond surfaces by hyperthermal atomic oxygen: A ReaxFF based molecular dynamics study

ReaxFF based reactive molecular dynamics simulations have been performed to gain an atomically detailed understanding of the etching of low index diamond surfaces exposed to energetic atomic oxygen collisions of the kind witnessed in the Low Earth Orbit (LEO) environment. ReaxFF simulations on small oxygen terminated diamond slabs indicated that a variety of functional groups such as ethers, peroxides, oxy radicals and dioxetanes can form on the surface, in agreement with earlier experiments and first principles based calculations. Successive oxygen collisions on larger reconstructed diamond surfaces showed that all the low index surfaces, namely diamond (1 0 0), (1 1 1) and (1 1 0) can be etched by hyperthermal atomic oxygen with diamond (1 0 0) showing the lowest etching rate and diamond (1 1 0) presenting the largest etching rate. The erosion yield of these surfaces is in good agreement with experimental results. The simulations performed here have been used to obtain an Arrhenius type rate law for the mass loss from these surfaces under such conditions. These simulations show that diamond thin films are promising materials for the surface of spacecraft exposed to LEO conditions and, in general, demonstrate the ability of ReaxFF to be used as an effective tool to screen or characterize materials for applications in extreme environments.