Spontaneous roughening: Fundamental limits in Si(100) halogen etch processing

A dynamical scanning tunneling microscopy and density functional theory study of the thermodynamic stability of halogen-terminated Si(100) surfaces is presented. Significant steric repulsions are shown to exist on all halogen-terminated Si(100) surfaces. These repulsions are the driving force for a roughening phenomenon, which is favored for all halogens except fluorine. Since roughening is an intrinsic property of these surfaces, it sets a lower bound on the atomic scale perfection that can be achieved using halogen etch processing.