Nanoindentation for measuring thin film mechanical properties is probably the most popular yet ill-understood method due to its inherent complexities. As opposed to burst pressure or microtensile tests of lithographed structures, where relatively uniform stress fields may be generated, the indentation-induced stress gradients can produce unique challenges. Because of the test's simplicity and ability to mechanically probe the smallest of scales, it is becoming increasingly applied. Five possible stages of deformation are suggested from Hertzian elastic to film delamination and double buckling. In particular metal films on harder substrates 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/m2. Current limitations of indentation-induced delamination measures of toughness involve large scatter associated with sensitivity of the fracture radius to the contact radius ratio.
|Original language||English (US)|
|Number of pages||9|
|State||Published - Nov 1999|
|Event||Proceedings of the 1998 ACTA Materiala Workshop on 'Materials Science and Mechanics of Interfaces' - La Jolla, CA, USA|
Duration: Oct 25 1998 → Oct 30 1998
Bibliographical noteFunding Information:
The authors gratefully appreciate support from the Office of Naval Research under Grants E-25-T46-51/ONR and N00014-91-J-1998 for three of us (W.W.G., D.E.K. and D.F.B.) from the Department of Energy under grants DOE/DE-FG02-96ER45574 and DOE/DEFG02-85ER13433A011 for four of us (W.W.G., A.F., N.T. and M.D.K.) and under grant NSF/CDR-8721551 for instrumentation usage. We would also like to thank Judy Schneider and Neville Moody of Sandia National Laboratories, Livermore, for the use of Fig. 7(b) .