Thickness-dependent fracture behaviour of flexible ZnO : Al thin films

Abstract

The effects of thickness on flexibility and crack initiation in ZnO : Al thin films sputter-deposited on polyethersulfone substrates have been investigated. With an increase in thickness, root-mean-square roughness and average crystallite size increase linearly. It is found that the higher the thickness, the lower is the strain required to initiate cracks in the film. The thinnest film (∼240 nm) exhibits a crack-initiating critical strain of 0.96% and a saturated crack density of 0.10 µm−1. A critical energy release rate of 68.5 J m−2 and a mode I fracture toughness of 3.2 MPa m0.5 are estimated for the films. These parameters are found to exhibit a linear dependence on film thickness.

Influence of Subsurface Hybrid Material Growth on the Mechanical Properties of Atomic Layer Deposited Thin Films on Polymers

“…The crack density was also analyzed by averaging the spacing between the cracks formed as a function of applied strain, shown in Figure 8b. For the ALD films processed at all temperatures, the crack density is observed to increase linearly with tensile strain, which is in agreement with the literature, when the crack density is far from saturation 27, 28. For comparison, the crack density for a 25 nm thick, Al 2 O 3 ALD coating on HSPEN deposited at 155 °C is ∼400 mm −1 27.…”

“…The crack formation in the central region of the sample test mount was observed using a Nikon SMZ‐10 stereoscope, equipped with an Infinity X‐32C camera, Lumenera. The nominal radius of curvature, r , at the center of the sample was calculated using Equation 5 28, 29 …”

“…The thickness of the film, t f , and the substrate, t s were approximated by the ellipsometry measurements and the thickness provided by the manufacturer, respectively. Using this procedure, the strain at the top of the film was determined using Equation 6 28, 30 …”

Possibilities of Increasing the Usability of Sputtered AZO Films as a Transparent Electrode

“…Currently, more attention is given to the use of TCOs on flexible polymer substrates, which entails additional requirements. In the case of flexible substrates, the higher film thickness results in the lower strain required to initiate cracks in the film . Moreover, the increase in the film thickness leads to lower film transmittance, prolongs the deposition time and thus causes an increase in production costs.…”

Bending effect on the resistive switching behavior of a NiO/TiO2 p–n heterojunction

“…A dramatic stress relaxation indicates that a group of parallel cracks in the NiO/TiO 2 layer begins to initiate and propagate at a bending radius of about 10 mm. The channel crack can easily form in grain boundaries, 36,37 and the diffusion paths of oxygen vacancies or metal ions are thus limited. As a result, the resistances in the HRS are slightly improved aer bending.…”