Figure 1

PEEM images captured from a video (available in the supplementary material [16]) of Ga droplet coalescence at $630°\mathrm{C}$. Liquid Ga appears bright against dark GaAs. (a) Droplets 1 and 2 are in close proximity at $t=0$. (b) At $t=3\mathrm{s}$, droplet 1 translates across the substrate and coalesces with droplet 2, leaving an exposed substrate arena which is associated with a shallow etch pit. This exposed arena region, enclosed by the frame in (b), is magnified in (c)–(f). Daughter droplet formation (c), and growth (d) is sometimes associated with surface ridges (R).Reuse & Permissions

Figure 2

MEM images captured from a video (in the supplementary material [22]) of Ga droplet coalescence at $650°\mathrm{C}$. In this imaging mode, concave surface features such as etch depressions appear bright relative to planar regions and convex droplets appear as dark circles surrounded by a bright concentric ring [19]. (a) At $t=0\mathrm{s}$, droplet 1 translates across the substrate and coalesces with droplet 2, leaving an exposed bright, circular etch depression region in (b). Note that droplet sizes are exaggerated in MEM and the true size of droplet 1, for example, closely approximates the shallow etch pit in (b). (c) Daughter droplets nucleate in the etch depression and appear as dark circles. (d) Eventually the etch pit planarizes.Reuse & Permissions

Figure 3

PEEM images of Ga droplet shrinkage and formation. (a) The sample is cooled below $T_c$ so that Ga droplets gradually shrink until they all eventually disappear in (b). Circled droplet 1 in (a) is the largest droplet and the last to disappear. On slowly heating the sample to $620°\mathrm{C}$, a new droplet is generated in the original position of droplet 1 (c). (d) This droplet was observed to be stable in the temperature range of $620–625°\mathrm{C}$ for several minutes with no other droplets appearing. (e) Increasing the temperature to $635°\mathrm{C}$ results an additional droplet appearing at the original position of droplet 2 in (a). (f) After a further minute at $635°\mathrm{C}$, $\sim 90\%$ of the new droplets reappearing correspond to previous droplet positions in (a) (circled droplets). The droplet enclose by a triangle has appeared at a new position.Reuse & Permissions