Influence of residual stresses on the mechanical properties of TiCxN1-x (x = 0, 0.15, 0.45) thin films deposited by arc evaporation

• Published in: Thin solid films 2000-08, Vol.371 (1-2), p.167-177
• Main Authors: KARLSSON, L, HULTMAN, L, SUNDGREN, J.-E
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Mechanical and acoustical properties; Physical properties of thin films, nonelectronic; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); TECHNOLOGY; TEKNIKVETENSKAP
• ISSN: 0040-6090; 1879-2731; 1879-2731
• DOI: 10.1016/s0040-6090(00)00996-2

The influence of residual stress state and composition on the mechanical properties of arc evaporated TiCxN1-x thin films been investigated. By controlling the flow ratios of the reactive gases, N2 and CH4, films with compositions x = 0 (TIN), x to approximately 0.15, and x to approximately 0.45 have been grown on cemented carbide substrates. The residual stress state was altered through variations in the negative substrate bias over the range 20 V=Vs=820 V. The intrinsic stress, sint, measured by the X-ray diffraction (XRD) sin2? method was compressive and increased with decreasing Vs and increasing x. The latter behavior is suggested to be due to increased effective stability of defect complexes when the carbon content increases. Maximum stress level was between -6 and -7 GPa and limited by interior cracking of the films. The increase in intrinsic stress was accompanied by an increase in XRD peak broadening due to inhomogeneous strains. The hardness, H, and Young's modulus, E, of as-deposited films were measured using the nanoindentation technique. Apparently linear correlations between sint and H were found for each film composition where H increased with x. The maximum H, 44 GPa, was thus obtained for the x to approximately 0.45 film with sint = -5.5 GPa. The lowest hardness for this composition was 35 GPa for a film with sint = -2.7 GPa. For the TiN films, a similar variation in hardness of 33 GPa at sint = -5.8 to 26 GPa at sint = -1.2 GPa was obtained. E was constant at approximately 610 GPa for most of the films, with a slight decrease in the films with the lowest sint values.