The use of nanoindentation techniques to measure nanoscale mechanical behavior is a new path of interest to researchers today. Load drops and displacement excursions can be utilized to measure activation volumes for dislocation events in single crystals, thin films, and nanoposts. Through the introduction of a new length-scale parameter, the dislocation wall spacing, a mechanism describing staircase yielding, is presented. The dislocation wall spacing can also be used to estimate activation volumes. Molecular dynamics simulations of nickel film indentation have been used to validate the origin of staircase yielding and also show consistent dislocation wall spacings. Additionally, stress relaxation experiments have been used to estimate activation volumes.
Bibliographical noteFunding Information:
Nickel single crystals were provided by S.V. Prasad of Sandia National Laboratories in Albuquerque, New Mexico. Sputtered gold film was provided by D.P. Adams, also of Sandia National Laboratories. N.R. Moody of Sandia National Laboratories, Livermore, California, is thanked for his many helpful discussions. The support from the U.S. Department of Energy through contract DE-AC04-94AL85000 and the National Science Foundation under