INTERFACE STRUCTURE AND SCHOTTKY-BARRIER HEIGHT OF BURIED COSI2/SI(001) LAYERS

The atomic interface structure of implanted buried layers in (100) oriented Si substrates has been characterized by quantitative high-resolution transmission electron microscopy on cross-section specimens. The buried layers were produced by high-dose Co+ ion implantation [100 and 200 keV Co+ ions, (1-2) X 10(17) cm-2] at 350-degrees-C and subsequent rapid thermal annealing at 750 and at 1150-degrees-C. Planar interface regions of high perfection with domains of different atomic interface structures, and interface steps, frequently with {111} facets, were observed. Comparison-with computer-simulated images for various interface models yields evidence for interface regions with six-fold and eight-fold coordination of the Co interface atoms. Furthermore, regions with interfaces showing a continuous transition as well as Co-rich interfaces were found. Measurements of the Schottky barrier heights have been performed and show smaller values for the upper CoSi2/n-Si(001) interfaces than for the lower ones. Possible correlations between the interface structures and the resulting electronic properties are discussed.