EQUILIBRIUM SHAPE OF SI

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 gamma(theta) for Si. Gamma(111) is the global minimum, with gamma(100) almost-equal-to 1.1 gamma(111) and all other cusps on the surface being relatively small. The experimental gamma(theta) is compared with theoretical predictions and earlier experiments. Step energies obtained from dgamma/dtheta are almost-equal-to 28 +/- 10 meV/atom on (100) and almost-equal-to 140 +/- 20 meV/atom on (111); these values are compared with scanning tunneling microscopy experiments.