Instability in Low-Temperature Molecular-Beam Epitaxy Growth of Si/Si(111)

Abstract

Using high-resolution low-energy electron diffraction we studied in situ low-temperature molecular-beam epitaxial growth of Si/Si(111). At $\ensuremath{\sim}275 \ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ and a deposition rate of $\ensuremath{\sim}7$ bilayers/min, a roughening evolution occurs after an initial transient layer-by-layer growth. It shows dynamic scaling characteristics with a roughness exponent $\ensuremath{\alpha}\ensuremath{\approx}1$ and an interface growth exponent $\ensuremath{\beta}=\frac{1}{4}$. More importantly, the average local slope is found to increase with time as $\ensuremath{\sim}\sqrt{\mathrm{ln}(t)}$. However, such a roughening behavior does not exist either at temperatures higher than 350 \ifmmode^\circ\else\textdegree\fi{}C or under a slower deposition rate of $\ensuremath{\sim}1$ bilayer/min. The phenomena are consistent with a statistical model of linear diffusion dynamics.