Dislocation Energetics and Pop-Ins in AlN Thin Films by Berkovich Nanoindentation

Abstract

Nanoindentation-induced multiple pop-ins were observed in the load-displacement curves when the mechanical responses of AlN films grown on c-plane sapphire substrates were investigated by using Berkovich indenters. No evidence of phase transformation is revealed by cross-sectional transmission electron microscopy (XTEM) and selected area diffraction (SAD) analyses. Instead XTEM observations suggest that these “instabilities” resulted from the sudden nucleation of dislocations propagating along the slip systems lying on the {0001} basal planes and the {10true1¯1} pyramidal planes commonly observed in hexagonal compound semiconductors. Based on this scenario, an energetic estimation of dislocation nucleation is made.

Nanomechanical properties of Bi2Te3 thin films by nanoindentation

“…In addition, since the pop-ins phenomena are randomly distributed on the loading curves associated with different stress rates, it is suggestive that the first pop-in event is not thermally activated. Instead, it might be due to similar plastic deformation activities observed in various materials [40,41]. Furthermore, the reverse discontinuities in the unloading segment of the load-displacement curve, the so-called ''pop-out'' event, commonly observed in Si which is attributed to pressure-induced phase transition [42] is not observed here.…”

Microstructure and Fracture Toughness of Fe–Nb Dissimilar Welded Joints

“…The P-h curve of Fe 2 Nb exhibits some serrations (indicated by black arrows) during loading, whereas that of α-Fe + Fe 2 Nb and α-Fe are quite smooth. These serrations signal the onset of plasticity in the indented materials [22][23][24]. The corresponding Fe 2 Nb impression ( Figure 5d) reveals some pile-up (indicated by black arrows), whereas the α-Fe + Fe 2 Nb impression ( Figure 5c) shows no obvious plasticity morphology.…”

Growth and thermal stability of TiN/ZrAlN: Effect of internal interfaces

“…More importantly, these multilayers show a stable and relatively high hardness (34 ± 1.5 GPa) even after isothermal annealing at 1150 o C. We suggest that the thermally stable semi-coherent interfaces between w-AlN and c-TMN domains offer both Koehler and coherency hardening similar to the isostructural interfaces between c-TiN and c-AlN. In addition, the non-isostructural semi-coherent interfaces provide an additional obstacles to dislocation glide due to the misorientation between the active glide planes (c-TiN {110} and w-AlN ) [47,48].…”