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TEM characterisation of indented TiN/SiNx multilayered coatings
|Magdalena Parlinska-Wojtan , Joao Carlos Cancio , Stephan Meier , Jörg Patscheider|
Empa, Laboratory for Nanoscale Materials Science, Ueberlandstrasse 129, Dübendorf 8600, Switzerland
Thin TiN/SiNx multilayered films composed of 100 repetitions of 5nm TiN and 0.5nm SiNx with a total thickness of 500nm were deposited by Closed Field Unbalanced magnetron sputtering on Si wafers at 300°C and -70V substrate bias. The TiN layers consisted of equiaxed, crystalline nanograins with a diameter of 5nm. Conversely, the SiNx layers were fully amorphous, providing a very sharp interface with TiN layers. The films were indented to 100, 250, 500 and 1000nm with a Berkovich indenter tip resulting in initial penetration depth between 20% and 200% of total film thickness. In this study nanoindentation technique was used to deliberately destroy the films, as 10% is the maximum penetration depth commonly agreed for hardness measurements. We investigate the induced defects and deformation mechanisms occurring upon plastic deformation. The microstructural observations were performed post-mortem by conventional and high resolution TEM on cross-sections prepared by FIB technique through the indentation imprint. For all indentation depths the TiN layers situated under the indenter tip apex showed evidence of severe compression. It is thus assumed that during indentation of multilayered coatings the deformation mechanism occurring is material flow. In all indented films, except the one with the lowest load, lateral cracks at the bottom of the coatings were observed determining the areas of highest stress concentration. At higher loads the coating delaminated from the substrate. Moreover, at 250 and 500nm indentation depth a median crack was generated in the film. Even for penetration depths exceeding the total film thickness the coating showed few interfacial cracks, while the multilayering remained intact. In the Si substrate deformation damages in form of nanocrystalline and amorphous regions in the vicinity of the film interface and dislocations forming a triangular shape under the indented film were observed.
Presentation: Oral at E-MRS Fall Meeting 2006, Symposium A, by Magdalena Parlinska-Wojtan
See On-line Journal of E-MRS Fall Meeting 2006
Submitted: 2006-05-12 08:37 Revised: 2009-06-07 00:44