INVESTIGATION OF THE ATOMIC INTERFACE STRUCTURE OF MESOTAXIAL SI/COSI2(100) LAYERS FORMED BY HIGH-DOSE IMPLANTATION

Aligned mesotaxial films of CoSi2 in monocrystalline (100) oriented Si substrates have been formed by high-dose ion implantation of Co, followed by a high temperature treatment. The atomic structures of both the lower and upper Si/CoSi2(100) interfaces of the buried CoSi2 layer have been investigated by high-resolution electron microscopy (HREM) combined with image simulations. A domain-like structure is observed consisting of areas with different interfaces. In order to derive the atomic configuration, image simulations of different proposed models are presented. By comparison of simulated images and HREM images, two different atomic structure models for the Si/CoSi2(100) interface have been found. In the first model, the interfacial Co atoms are six-fold coordinated and the tetrahedral coordination and bond lengths of silicon atoms are everywhere maintained. In the second model, we found evidence for a 2 x 1 interface reconstruction, involving a difference in composition. The interfacial Co atoms are seven-fold coordinated. It is shown that the boundaries between the domains are associated with interfacial dislocations of edge-type with Burgers vectors b = a/4<111> inclined and b = a/2<100> parallel to the interfacial plane.