Scale effects of nanomechanical properties and deformation behavior of Au nanoparticle and thin film using depth sensing nanoindentation

Abstract

SummaryNanoscale research of bulk solid surfaces, thin films and micro- and nano-objects has shown that mechanical properties are enhanced at smaller scales. Experimental studies that directly compare local with global deformation are lacking. In this research, spherical Au nanoparticles, 500 nm in diameter and 100 nm thick Au films were selected. Nanoindentation (local deformation) and compression tests (global deformation) were performed with a nanoindenter using a sharp Berkovich tip and a flat punch, respectively. Data from nanoindentation studies were compared with bulk to study scale effects. Nanoscale hardness of the film was found to be higher than the nanoparticles with both being higher than bulk. Both nanoparticles and film showed increasing hardness for decreasing penetration depth. For the film, creep and strain rate effects were observed. In comparison of nanoindentation and compression tests, more pop-ins during loading were observed during the nanoindentation of nanoparticles. Repeated compression tests of nanoparticles were performed that showed a strain hardening effect and increased pop-ins during subsequent loads.

Nanoscale effects on the thermal and mechanical properties of AlGaAs/GaAs quantum well laser diodes: influence on the catastrophic optical damage

“…Whereas the stress-strain relationships on the microscale have been found to be very similar to those of the bulk, remarkably high sub-micron yield strengths have been reported for different materials [47,[50][51][52]. This has been rationalized in terms of different mechanisms, such as the Hall-Petch [50,53,54] or modified confined layer slip (CLS) models [51,55]. These schemes, suggested for different materials, describe the yield strength as defined by the characteristic lowest dimension of the system (h).…”

“…We have already argued about their capital influence on the thermal conductivity, but now is the time to focus on the mechanical behaviour [47][48][49]. Whereas the stress-strain relationships on the microscale have been found to be very similar to those of the bulk, remarkably high sub-micron yield strengths have been reported for different materials [47,[50][51][52]. This has been rationalized in terms of different mechanisms, such as the Hall-Petch [50,53,54] or modified confined layer slip (CLS) models [51,55].…”

Friction, wear and mechanical behavior of nano-objects on the nanoscale

“…Deformation, instead occurs through grain rotation and grain boundary sliding which becomes easier in the absence of dislocations. A combination of material defects, such as existing cracks and spaces within nano-objects made of layered material and dislocations formed with stacking faults can also prevent observation of enhanced hardness [16,51].…”

“…Mechanical properties can either be reduced or similar to bulk in some cases or enhanced as material dimensions go from the macro-to nanoscale [51].…”

“…In studies of bulk solid surfaces [55][56][57][58][59][60][61] and thin films [51,[62][63][64][65] made of various materials including Al, Au, Ag, Cu, GaAs, GaP, Si, Ti, ZnSe and Ni, scale effects on hardness with respect to depth of penetration and decreasing film thickness have been reported. For example, Pharr and Oliver [57] and Bhushan et al [59], found that decreasing indentation depth resulted in higher hardness of Ag and Si surfaces, respectively.…”