AL GROWTH ON SI(001) OBSERVED BY SCANNING-TUNNELING-MICROSCOPY

We observed the initial stages of Al growth on Si(001) using scanning tunneling microscopy. The Al films were deposited under various substrate conditions; on a clean surface at room temperature (RT) and 500 degrees C, and on a hydrogen-terminated surface at RT. At RT on a clean surface, rectangular patches of Al elongating in the [110] direction were formed on 2 x 2 array terraces above the first 0.5 monolayers, in addition to three dimensional island formation. On the other hand, at 500 degrees C, Al or A-Si clusters, well ordered one-dimensionally in the [110] or [($) over bar 110] direction, appeared. Arrangement of the clusters exhibited a variety of local symmetries. Also, we deposited Al on a H-terminated Si(001)-3 x 1 surface. The scanning tunneling microscopy (STM) image showed a characteristic growth pattern of the Al film and higher density of nuclei than that on a clean surface.