STRUCTURAL STUDIES OF AL/SI(100) BY LEED

The structures of Al-adsorbed Si(100) surfaces were studied by observing patterns, line profiles and intensity-versus-energy (I-V) curves of low-energy electron diffraction (LEED). Al-adsorbed 2 x 1, 2 x 2 and 2 x 3 structures were observed as a function of Al coverage and the substrate temperature. After deposition of less than 0.25 ML of Al below 300-degrees-C, we observed an Al-2 x 1 LEED pattern whose I-V curves were different from those of the clean Si(100)2 x 1 surface. For 0.5 ML deposition of Al, a 2 x 2 phase appeared at a substrate temperature of 100-degrees-C. At about 0.3 ML, a 2 x 3 structure was formed at 300-degrees-C, which was confirmed by observing the LEED pattern and line profiles. It was also found that the main features of I-V curves of the Al-2 x 2 surface and those of the in-2 x 2 surface are verv much alike. This reflects the fact that their geometric structures are also alike.