Roughening and Preroughening of Diamond-Cubic {111} Surfaces

Abstract

AbstractUsing a new solid-on-solid model that correctly takes into account the diamond-cubic crystal structure, both a roughening transition at temperature TR and a distinct preroughening transition at TPR≈0.43TR are found to exist on {111}surfaces of diamond-cubic materials. Results are presented for height-difference correlation functions, surface specific heats, step energies, etch rates, and a preroughening order parameter. Preroughening appears to arise naturally in our nearest-neighbor bond model from the entropic freedom available in the non-trivial crystal structure suggesting that preroughening may be more common than previously anticipated. Preroughening is shown to dramatically lower step energies and step-energy anisotropy on the {111} surface. Preroughening of Si{111} may have been seen in experiments by Noh et al. [Phys. Rev. B 48, 1612 (1993)].