Small voids are formed in Si by MeV He implantation and annealing. We measure the equilibrium shape of these voids and hence extract the surface energy curve γ(θ) for Si. γ(111) is the global minimum, with γ(100)≊1.1γ(111) and all other cusps on the surface being relatively small. The experimental γ(θ) is compared with theoretical predictions and earlier experiments. Step energies obtained from dγ/dθ are ≊28±10 meV/atom on (100) and ≊140±20 meV/atom on (111); these values are compared with scanning tunneling microscope experiments.

• Received 12 October 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.1643