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

Diamond-like carbon (DLC) coatings were fabricated under high vacuum at low 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 atomically flat hydrogenated amorphous carbon (a-C:H) coatings with a sp(3) content of typically 20%. RBS measurements show that coatings produced at high acceleration voltage have impurities of carbon in the near-surface region of the silicon substrate as well as silicon impurities in the DLC coating at the interface. The penetration depth of the impurities is energy dependent. Nanoindentation measurements provided hardness figures of up to 18 GPa combined with high elasticity values of 90%. Hardness and elasticity values and the sp(3) content were measured to be proportional to the acceleration energy. An interface layer was observed with transmission electron microscopy indicating atomic interlocking between the carbon coating and the silicon substrate. The results highlight the opportunity to produce a-C:H coatings with high elasticity by direct ion deposition at low temperature. (C) 2014 Elsevier B.V. All rights reserved.