Direct methods were applied to transmission electron diffraction data to solve the previously unknown In on Si(111)4x1 surface structure. The structure consists of zig-zag chains of In atoms separated by regions of silicon including dimer chains (Fig 1.). The 4x1 structure is one of several stable surface structures formed with increasing In coverages on the Si(111) surface. The √3x√3 structure consists of 1/3 of a monolayer of In, the √31x√31 occurs at a slightly higher coverage and the 4x1 structure appears before the formation of In islands on the surface . While the √3x√3 surface has been extensively studied, relatively little is known about the √31x√31 and 4x1 structures. Knowledge of the atomic positions in the 4x1 structure is an important step in understanding metal/semiconductor epitaxy and interface formation.
Two data sets were used in this study -- the first recorded on film and reduced in Tokyo, the second recorded on Imaging Plate in Tokyo and reduced at Northwestern. Twenty-seven independent intensities were measured.