Sub-atomic-layer epitaxy of Si using Si2H6

We have recently proposed a sub-atomic-layer epitaxy technique (SALE) with which Si is grown by sub-monolayer-by-sub-monolayer from Si2H6 on Si(001). With a newly incorporated surface thermal excitation process, the growth surface is atomically flattened every growth cycle without depending on the saturation coverage of Si2H6. To optimize SALE growth conditions, the surface flattening reaction process has been investigated by observing time-dependent dynamic changes in reflection high energy electron diffraction (RHEED) patterns during annealing Si2H6-exposed Si(001) surfaces using a charge-coupled-device camera. Upon annealing, a spotty 2 × 1 pattern of the initial surface changes to a streaky 2 × 1 pattern and then changes to a spotty 2 × 1 pattern again. In the period when the RHEED pattern is streaky, terraces are considered to emerge and grow by adatom migration accompanied by or following hydrogen desorption. On the basis of these RHEED studies, the thichness distribution profiles of films, grown by the SALE method using an Ar+ ion laser as a surface excitation source, have been investigated. From the results of the RHEED and SALE growth studies, the relation between the surface excitation conditions and the surface flattening reaction process in the SALE method is obtained.