Absolute surface energy determination

Experimental determination of absolute surface energies remains a challenge. We propose a simple method based on two independent measurements on 3D and 2D equilibrium shapes completed by the analysis of the thermal fluctuation of an isolated step. Using then basic equations (Wulff’ theorem, Gibbs–Thomson equation, thermodynamics fluctuation of an isolated step) allows us to extract the absolute surface free energy of a singular face. The so-proposed method can be applied when (i) all orientations exist on the equilibrium shape, (ii) the surface stress is isotropic. This procedure is applied to the case of Si(1 1 1) where we find 0.59 J m−2 ⩽ γ(1 1 1) ⩽ 0.83 J m−2 at 1373 K.