Silicon interaction with low-electronegativity metals: Interdiffusion and reaction at the Ca/Si(111) interface

We present the first photoemission study of reactions which occur at an alkali-earth--silicon interface. Room-temperature results indicate extensive atomic interdiffusion with substantial ionic bonding. Analysis of the Si 2p core line shape, the Ca 3p core levels, the many-body losses, and the valence bands shows that the first reaction product (1< or =THETA< or =12 A) corresponds to a weakly metallic Ca-Si phase. A second component is Ca-rich but has Si present in two different bonding configurations. Core line-shape analysis facilitates evaluation of interface atomic concentrations and discussions of morphology