A transmission electron microscopy study of the deformation behavior underneath nanoindents in nanoscale Al–TiN multilayered composites

Abstract

Nanoscale multilayered Al–TiN composites were deposited using the dc magnetron sputtering technique in two different layer thickness ratios, Al : TiN = 1 : 1 and Al : TiN = 9 : 1. The Al layer thickness varied from 2 nm to 450 nm. The hardness of the samples was tested by nanoindentation using a Berkovich tip. Cross-sectional transmission electron microscopy (TEM) was carried out on samples extracted with focused ion beam from below the nanoindents. The results of the hardness tests on the Al–TiN multilayers with two different thickness ratios are presented, together with observations from the cross-sectional TEM studies of the regions underneath the indents. These studies revealed remarkable strength in the multilayers, as well as some very interesting deformation behavior in the TiN layers at extremely small length scales, where the hard TiN layers undergo co-deformation with the Al layers.

Keywords:

• multilayer
• nanocomposite
• nanoindentation
• nanomechanics
• transmission electron microscopy
• focused ion beam

Acknowledgements

The authors would like to acknowledge the support of the Office of Basic Energy Sciences of the Department of Energy, United States Government. The help and technical expertise of J.K. Baldwin in the deposition of the thin films is also gratefully acknowledged. Darrick Williams is acknowledged for his help with some XRD measurements. The authors would also like to thank Prof. J.P. Hirth for many helpful discussions.