STRUCTURE OF (SQUARE-ROOT-3 X SQUARE-ROOT-3) R 30-DEGREES-B AT THE SI INTERFACE STUDIED BY GRAZING-INCIDENCE X-RAY-DIFFRACTION

The boron-induced (7/8 × 7/8) R30°reconstruction at the Si interface has been investigated by grazing incidence x-ray diffraction. The in-plane projected struture is found from the structure factors near zero perpendicular momentum transfer. At the a-Si/Si (111) interface, boron atoms at 1/3 ML are substituted for silicon atoms, thus forming a (7/8 × 7/8) R30°lattice and the boronsilicon bond is contracted compared with the siliconsilicon bond. Even at the interface between a solid phase epitaxial Si (111) layer and a Si (111) substrate, the boron-induced (7/8 × 7/8) R30°reconstruction has also been observed and the structure is similar to that observed at the a-Si/Si (111) interface.