Nanoindentation-induced defect-interface interactions: Phenomena, methods and limitations

Nanoindentation for measuring thin film mechanical properties is probably t he most popular yet ill-understood method due to its inherent complexities. As opposed to burst pressure or microtensile tests of lithographed structu res. where relatively uniform stress fields may be generated, the indentati on-induced stress gradients can produce unique challenges. Because of the t est's simplicity and ability to mechanically probe the smallest of scales, it is becoming increasingly applied. Five possible stages of deformation ar e suggested from Hertzian elastic to film delamination and double buckling. In particular metal films on harder substrares are emphasized where it is shown that dislocation nucleation and arrest are only partially understood. Later stages of film delamination are illustrated with Cu/SiO2/Si where it is shown that the true work of adhesion is 0.6 J/m(2). Current limitations of indentation-induced delamination measures of toughness involve large sc atter associated with sensitivity of the fracture radius to the contact rad ius ratio. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Lt d. All rights reserved.