In situ TEM nanoindentation of nanoparticles

The deformation behavior of nanoparticles continues to be an exciting area for materials research. Typically, nanoparticles show a conspicuous lack of dislocations, even after significant deformation. Therefore, it has been suggested that dislocations cannot exist or/do not play a role on the deformation of nanoparticles. In situ TEM nanoindentation is a critical tool for addressing this issue because it allows for the deformation to be monitored in real time. In this article, we discuss some of the experimental needs and challenges for performing in situ nanoindentation TEM experiments on nanoparticles. In addition, we show both diffraction contrast and phase contrast in situ TEM nanoindentation experiments on silver nanoparticles with diameters below 50 nm. Evidence of the presence of dislocations was observed during deformation, but upon unloading dislocations disappeared.

► In situ TEM nanoindentation experiments were performed on silver nanoparticles ranging from 10 nm to 35 nm.
► In situ TEM nanoindentation experiments were carried out under diffraction-contrast and phase-contrast.
► Under diffraction-contrast conditions, contrast bands appear in the nanoparticle upon nanoindentation. However, whether these contrast bands are bend contours or dislocations remain unconfirmed.
► Under phase-contrast conditions, dislocations were observed to appear within the nanoparticle upon nanoindentation.
► Upon removal of the nanoindentation holder, dislocations disappear, which is due to the fact that they unstable in nanoparticles below a critical size.