Morphologies and kinetics of a dewetting ultrathin solid film

The surface evolution model based on a geometric partial differential equation is used to numerically study the kinetics of dewetting and the dynamic morphologies for the localized pinhole defect in the surface of an ultrathin solid film with the strongly anisotropic surface energy. Depending on the parameters such as the initial depth and width of the pinhole, the strength of the attractive substrate potential and the strength of the surface-energy anisotropy, the pinhole may either extend to the substrate and thus rupture the film, or evolve to the quasiequilibrium shape while the rest of the film surface undergoes a phase separation into a hill-and-valley structure followed by coarsening. Emergence of the quasiequilibrium shape and the termination of a dewetting are associated with the faceting of the pinhole tip. Overhanging (nongraph) morphologies are possible for deep, narrow (slitlike) pinholes.

Figure 1

Kinetics (rate) data for the deep pinhole $\left(d=0.9\right)$. ${ϵ}_{\gamma }=1/12$, $\beta =0$. Line slope equals the rate of the tip evolution. Solid line: $r=0.1$. Dash line: $r=0.02$. (a) Wide pinhole $\left(w=2\right)$. (b) Intermediate pinhole $\left(w=1\right)$. (c) Narrow pinhole $\left(w=0.15\right)$.

Figure 2

Same as Fig. 1, but for the shallow pinhole $\left(d=0.5\right)$.

Figure 3

Kinetics data for the deep, wide pinhole. $r=0.1$. Solid line: ${ϵ}_{\gamma }=1/12$, $\beta =0$. Dash line: ${ϵ}_{\gamma }=1/12$, $\beta =10°$. Dash-dot line: ${ϵ}_{\gamma }=1/8$, $\beta =0$. Dash-dash-dot-dot line: ${ϵ}_{\gamma }=1/14$, $\beta =0$.

Figure 4

Surface morphologies for the deep pinhole. $r=0.1$, ${ϵ}_{\gamma }=1/12$, $\beta =0$. The depth $\left(d\right)$ and the width $\left(w\right)$ of the pinhole at $t=0$ are defined. Solid, dash, dash-dot line: $w=2,1,0.15$, respectively. Inset: the magnified view of the dewetting region for $w=2,1$.

Figure 5

Magnified view of the transient, overhanging surface morphology for the deep, narrow pinhole from Fig. 4. Dash line: the surface at $t=0$.

Figure 6

Surface morphologies for the shallow pinhole. $r=0.1$, ${ϵ}_{\gamma }=1/12$, $\beta =0$. (a): $w=2$, (b): $w=1$, (c): $w=0.15$. Dash line: the surface at $t=0$.

Figure 7

Surface morphology for the shallow, wide pinhole. $r=0.1$, ${ϵ}_{\gamma }=1/12$, $\beta =10°$. Dash line: the surface at $t=0$.

Figure 8

Contour plot of the dewetting factor $\text{exp}\left(-z/r\right)/r^2$.