Buckling instability and adhesion of carbon layers

Abstract The mechanical properties of thin coatings are closely coupled with the preparation techniques used. In carbon layers deposited by electron beam and ion beam techniques high compressive stresses were measured and these stresses cause debonding of the layer. In some cases amazing structures and shapes of the debonded regions were observed: wavy wrinkles with well-defined widths and shapes. The nucleation and growth of these wrinkles is caused by a very well-defined combination of internal strain, Young's modulus, coating thickness and adhesion energy. This may be used to estimate the internal strain as well as the adhesion energy. For the i-C (where i signifies the use of an ion beam) layers 200 nm thick that were investigated internal stresses of 3–6 GPa and adhesion energies in the range of 4–7 N m−1 were estimated. These adhesion energies are more than an order of magnitude higher than those measured previously.