Längenskaleneffekte im Ermüdungsverhalten von Cu Schichten bei hoch zyklischer Belastung

• Applicant: Professorin Dr. Cynthia A. Volkert
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: from 2011 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 192822769

• Final Report Year: 2016

Final Report Abstract

In this study we have shown that creep is a limiting factor for the fatigue performance of thin films at high cycle numbers. Creep sets in for strain amplitudes that fall below the film thickness dependent threshold for dislocation glide. At sufficiently high cycle numbers, grooves will form at the grain boundaries even at very small strain amplitudes due to dislocation climb at the grain boundaries. For films that are used in applications where a smooth film surface is important, our study has shown that cyclic loading will lead to degradation of the performance. Thus, although fatigue life can be improved by decreasing the film thickness, a new limit has been discovered due to grain boundary creep that must also be considered when designing devices. Furthermore, a fatigue failure map for Cu thin films has been generated based on our data for Cu thin films and on mechanistic equations for damage formation.

Publications

• In situ nanomechanical testing in focused ion beam and scanning electron microscopes. Rev. Sci. Instrum. 82, 063901 (2011)
  D. S. Gianola, A. Sedlmayr, R. Mönig, C. A. Volkert, R. C. Major, E. Cyrankowski, S. A. S. Asif, O. L. Warren and O. Kraft
  
• Influence of crystal orientation on pattern formation of focused-ion-beam milled Cu surfaces. Phys. Rev. B 84, 035451 (2011)
  M. Lenius, R. Kree, and A. Volkert
  
• Mechanical behavior of nanoscale Cu/PdSi multilayers. Acta Mat. 61, 4984 (2013)
  I. Knorr, N.M. Cordero, E.T. Lilleodden, and C.A. Volkert
  
• Mechanismen und Größeneffekte von Ermüdungsschädigungen in dünnen Kupferfilmen bei sehr hohen Zyklenzahlen, Dissertation Göttingen 2013
  Clemens Trinks
  
• Transition from dislocation glide to creep controlled damage in fatigued thin Cu films. J. Appl. Phys. 114, 093510 (2013)
  C. Trinks and C. A. Volkert
  
• Influences of Ta passivation layers on the fatigue behavior of thin Cu films. Mat. Sci. Eng. A 610, 33 (2014)
  D. Wang, P. A. Gruber, C. A. Volkert, and O. Kraft