Bending flexibility, kinking, and buckling characterization of ZnO nanorods/nanowires grown on different substrates by high and low temperature methods

Abstract

Nanomechanical tests of bending flexibility, kinking, and buckling failure characterization of vertically aligned single crystal ZnO nanorods/nanowires were performed quantitatively by nanoindentation technique. These nanostructures were grown by the vapor liquid solid ͑VLS͒ method, a relatively high temperature approach, and the aqueous chemical growth ͑ACG͒ method, a relatively low temperature approach on different substrates, including SiC and Si. The first critical load at the inflection point found for the ZnO nanorods/nanowires grown by ACG method was 105 N on the SiC substrates and 114 N on the Si substrates. The corresponding buckling energies calculated from the force-displacement curves were 3.15ϫ 10 −12 and 2.337ϫ 10 −12 J, respectively. Similarly, for the samples grown by the VLS method, the first critical load at the inflection point and the corresponding buckling energies were calculated from the force-displacement curves as 198 N and 7.03ϫ 10 −12 J on the SiC substrates, and 19 N and 1.805ϫ 10 −13 J on the Si substrates. Moreover, the critical buckling stress, strain, and strain energy were also calculated for all samples. The strain energy for all samples was much less than the corresponding buckling energy. This shows that our as-grown samples are elastic and flexible. The elasticity measurement was performed for all the samples before reaching the first critical and kinking inflection point, and we subsequently observed the bending flexibility, kinking, and buckling phenomena on the same nanorods/nanowires. We observed that the loading and unloading behaviors during the bending test of the as-grown samples were highly symmetrical, and also that the highest point on the bending curves and the first inflection and critical point were very close. ZnO nanorods/nanowires grown on SiC by the ACG method, and those grown by the VLS method on Si substrates, show a linear relation and high modulus of elasticity for the force and displacement up to the first inflection and critical point. The results also show that the elasticity of the ZnO single crystal is approximately linear up to the first inflection point, is independent of the growth method and is strongly dependent on the verticality on the surface of the substrates. In addition, the results show that after the first buckling point, the nanorods/nanowires have plasticity, and become more flexible to produce multiple kinks.

Nanoscale piezoelectric response of ZnO nanowires measured using a nanoindentation technique

“…Figure 5 shows the load-displacement curve for the nanoindentation of NWs deposited on paper substrate. It is possible to observe that with a maximum load of 50 µN, the NW column is in stable equilibrium in the straight position, i.e., there is no buckling [29][30]. The experiment also shows that, during the time that the nanoindenter applies the maximum force, the curves present a creep of 35 nm.…”

The effect of oxygen-plasma treatment on the mechanical and piezoelectrical properties of ZnO nanorods

“…For the ZnO NRs coated substrates the penetration of the tip was about ~650 nm. The comparison of load-displacement curves for both NRs samples show that the oxygen plasma treated samples are stiffer than the as grown ones, because the tip needs to apply more force after 300 nm penetrations to buckle/bend [28][29][30] the plasma-treated nanorods.…”

Synthesis, Characterization and Applications of Metal Oxide Nanostructures

“…These include parameters like hardness, stiffness, toughness, yield strength, piezoelectric constant; Young's and bulk moduli, and adhesion to the substrate [34][35][36]. It is important to point out that if the diameter and length of the nanostructure varies then it also affects the mechanical properties [34][35][36]. Therefore in order to have efficient and reliable piezoelectric devices, the characterization of its mechanical properties is the backbone.…”

“…Therefore in order to have efficient and reliable piezoelectric devices, the characterization of its mechanical properties is the backbone. That is why mechanical properties of different materials have been extensively studied [34][35][36][37][38][39][40][41][42][43].…”

“…So in such a case the mechanical characterization of nanostructures plays an important role. These include parameters like hardness, stiffness, toughness, yield strength, piezoelectric constant; Young's and bulk moduli, and adhesion to the substrate [34][35][36]. It is important to point out that if the diameter and length of the nanostructure varies then it also affects the mechanical properties [34][35][36].…”