Epitaxial growth of Al on Si by thermal evaporation in ultra-high vacuum: growth on Si(100)2 × 1 single and double domain surfaces at room temperature

Abstract

Growth of Al on Si(100) in ultra-high vacuum was investigated using in situ RHEED, LEED and AES and ex situ TEM and SEM. The substrates were kept at room temperature during growth. Al was found to grow epitaxially on Si(100)2 × 1 with the orientation relationship Al(110)//Si(100). TEM and RHEED showed that the Al layer had two types of (110)-oriented domains that are 90° rotated with respect to each other in accordance with the following relations Al[001]//Si[011] or Si[01̄1]. RHEED observations during growth demonstrated a continuous change from the original Si(100)2 × 1 pattern to a 1 × 1 pattern after deposition of 2 monolayers (ML). At an Al coverage θ Al = 3 ML, a faint and broad Al-bulk diffraction related intensity was observed in RHEED while a clear Al-bulk diffraction pattern became visible after ~ 4 ML, indicating three-dimensional growth of Al islands. The decay in the Si AES peak-to-peak intensity versus θ A1 could only be modelled by a layer-by-layer growth mode up to θ A1 = 4 ML. On an off-oriented, essentially single-domain Si(100)2 × 1 surface, an almost single-domain, monocrystalline Al(110) layer was obtained with only a few 90° rotated crystals. Thus the observed Al crystal domains are related to the Si(100)2 × 1 surface domains. The results are explained in terms of Al dimerization on the Si surface and epitaxial growth on the dimerized layer. A growth sequence leading to the growth of Al(110) crystals is also suggested.