Quantitative in situ nanoindentation in an electron microscope

We report the development of a method for quantitative, in situ nanoindenta tion in an electron microscope and its application to study the onset of de formation during the nanoindentation of aluminum films. The force-displacem ent curve developed shows the characteristic "staircase" instability at the onset of plastic deformation. This instability corresponds to the first ap pearance of dislocations in a previously defect-free grain. Plastic deforma tion proceeds through the formation and propagation of prismatic loops punc hed into the material, and half loops that emanate from the sample surface. These results represent the first real time observations of the discrete m icrostructural events that occur during nanoindentation. (C) 2001 American Institute of Physics.