Ordering of amorphous silicon during solid-phase epitaxy studied by scanning tunneling microscopy

The early stages of silicon solid-phase epitaxy (SPE) on the Si(111) surface are studied by scanning tunneling microscopy (STM). It is shown that an amorphous layer with thickness around two bilayers deposited on the silicon surface transforms in a polycrystalline layer with extremely small grain size (about 2–3 nm) after heating to 430 °C. The atomic-resolution STM imaging of such a disordered surface allows us to extract lateral coordinates of the upper-layer atoms. The application of the pair-distribution-function formalism reveals anisotropy in the orientational order that might indicate that the SPE occurs preferably in the step direction.