Ultra-smooth diamond-like carbon coatings with high elasticity deposited at low temperature by direct ion beam deposition

Diamond-like carbon coatings were fabricated under high vacuum at room temperature using a direct ion beam deposition technique based on a penning ion source. Post acceleration and electrostatic scanning were applied to form adhesive and laterally homogenous coatings across 50 mm using ion energies from 3.0 to 10.5 kV. The deposition rate was set to 0.4 nm s^-1 to prevent heating of the coating and substrate. Structural, physical and chemical analyses revealed the formation of amorphous atomically flat hydrogenated amorphous carbon (a-C:H) coatings with a sp³ content of typically 20 %. Nanoindentation measurements provided hardness figures of up to 18 GPa combined with high elasticity values of 90 %. Hardness and elasticity values and the sp³ content were measured to be proportional to the ion energy. Furthermore, a growing interface layer was observed with transmission electron microscopy images indicating atomic interlocking between the carbon coating and the silicon substrate. The result highlight the opportunity to produce a-C:H coatings with high elasticity with direct ion deposition at room temperature.