Young's modulus of (Ti,Si)N films by surface acoustic waves and indentation techniques

Ti1-xSixNy films with Si contents up to 17.5 at.% and N contents close to 50 at.% were prepared by r.f. reactive magnetron sputtering. Film densities are within the range 3.4-5.1 g/cm(3). X-Ray diffraction patterns indicated the formation of two crystalline phases. In the case of low surface mobility. a metastable (Ti, Si)N phase was formed, where Si atoms occupied Ti positions. With increasing surface mobility, a crystalline TiN phase was observed. This behaviour may be explained by the occurrence of Si3N4 segregation, leading to the formation of a nanocomposite film of the type nc-TiN/nc-(Ti,Si)N/a-Si3N4, although the presence of Si3N4 phase is difficult to prove. In some of the films, a mixture of the (Ti,Si)N metastable phase with the TiN phase was observed, which indicates that the segregation of both TiN and Si3N4 phases is not complete. The Young's modulus, Er, of each coating was evaluated using both indentation tests and the surface acoustic waves (SAW) method. For most samples, the results obtained by these two methods are in good agreement. Some differences were observed in films prepared with a bias voltage of -50 V and Si contents higher than 5.9 at.%. For these samples, indentation values of approximately 10-20% higher than those obtained from SAW were found. This discrepancy is related to the nanostructure of these coatings, and it should be pointed out that the SAW results are strongly correlated with the density of the material. (C) 2002 Elsevier Science B.V. All rights reserved.