Geometric structure of the nisi₂---si(111) interface: an x-ray standing-wave analysis

Abstract

The atomic structure at the interface of single-crystal NiSi₂ films on Si(111) has been determined with X-ray standing waves. Two types of films have been investigated, one with the same crystal orientation as the substrate (A type), and the other with its orientation 180° rotated about the surface normal (B type). For both orientations, the Ni atoms at the interface are found to be seven-fold coordinated. The bonds across the interface are contracted by 0.04 ± 0.05 Å for the A-type film and 0.11 ± 0.03 Å for the B-type film. For the first time the strain in an overlayer has been measured by the X-ray standing-wave technique, using, a moire effect between the overlayer lattice planes and the X-ray standing-wave field. The (111) interplanar distance in NiSi₂ is found to be contracted by 0.4%.