Relationship between mechanical properties and coefficient of friction of sputtered a-C/Cu composite thin films

The article reports on properties of a-C films containing different amount of Cu. Films were sputtered by unbalanced magnetron from a graphite target with Cu fixing ring in argon under different deposition conditions. Relationships between the structure, mechanical properties, macrostress sigma and coefficient of friction (CoF) mu of a-C/Cu films sputtered on Si substrates were investigated in detail. Besides, a special attention was concentrated on investigation of the effect of a deposition rate an of the a-C/Cu film on its hardness H and macrostress sigma. Four main issues were found: (1) the addition of Cu into a-C film strongly influences its structure and mechanical properties, i.e. the hardness H, effective Young's modulus E* macrostress (sigma and CoF, and makes it possible to form electrically conductive films; here E*= E/(1- v(2)), E is the Young's modulus, and v is the Poisson's ratio, (2) the hardness H and compressive macrostress a of the a-C/Cu film decrease with increasing a(D) due to decreasing of total energy ET delivered to the film during its growth, (3) hard a-C/Cu films with low value of CoF (mu approximate to 0.1) can be sputtered at high deposition rates aD ranging from similar to 10 to similar to 80 nm/min, and (4) CoF decreases with increasing (i) hardness H and (ii) resistance of film to plastic deformation characterized by the ratio H-3/E*(2) but only in the case when compressive macrostress sigma is low. (C) 2008 Elsevier B.V. All rights reserved.