Figure 1

(a) The geometry of the deformed sol-gel-derived film on a substrate. (b) Plane SEM images showing representative wrinkle patterns in the form of skeletal branches for the ZnO film $(\text{film thickness}=85\mathrm{nm})$ annealed at 150 °C for 18 h (scale bars are from left: 50 and 2 μm, respectively). (c) A cross-sectional FESEM image of the wrinkle patterns of the film. The inset is a magnified FESEM image of the wrinkled region.Reuse & Permissions

Figure 2

Comparisons of the theoretical predictions with the different experimental data. Symbols are used to indicate the different experimental data, and the three different lines corresponding to the theoretical results are identified by the slopes referred to in the inset. The dark square symbols, circle, and triangle symbols refer to the wrinkle patterns of the ZnO films $(\text{film thickness}=85\mathrm{nm})$ annealed at 150 °C, for 2, 5, and 18 h, respectively.Reuse & Permissions

Figure 3

SEM images of the temporal variation of the skeletal branches of the ZnO film annealed at 150 °C. (a) Wrinkle pattern of 85-nm-thick film annealed for 2 h, (b) annealed for 10 h, (c) annealed for 18 h, and (d) wrinkle pattern of 157-nm-thick film annealed for 2 h, (e) annealed for 10 h, and (f) annealed for 18 h. Scale bars denote 10 μm.Reuse & Permissions

Figure 4

(a) Plane AFM image of skeletal wrinkles of 85-nm-thick film annealed at 150 °C for 5 h $(40\mu \mathrm{m}\times 40\mu \mathrm{m})$. The FFT image for the wrinkles is given in the upper right inset, and the cross-sectional profile is shown in the lower inset. (b) Comparison of the theoretical predictions with the experimental results of the average length of skeletal branches. Solid lines and dotted lines are used for the prediction of the wrinkles in the 157-nm-thick film $(\text{average amplitude}=42\mathrm{nm})$ and in the 85-nm-thick film $(\text{average amplitude}=29\mathrm{nm})$, respectively. Dark and open symbols are for the experimental results of the wrinkles in the 157-nm-thick film and in the 85-nm-thick film. The inset is a simplified two-dimensional model of hexagonally interconnected skeletal branches. (c) Comparison between theoretical predictions with experimental results of the rms. The solid and dotted lines represent the predictions, while the dark and open symbols represent the experimental results as in the caption of (b). Volumetric evaporation rate of the solvent per unit area of the film is assumed as $0.1\mathrm{nm}∕\mathrm{h}$.Reuse & Permissions