HIGH-RESOLUTION ELECTRON-MICROSCOPY IMAGE-CONTRAST AT THE COSI2/SI(111) INTERFACE

The atomic structure of the CoSi2/Si(111) interface, investigated by high-resolution electron microscopy (HREM) combined with image simulations is considered. The contrast in bulk CoSi2 is studied using a simple linear imaging theory, establishing the relation between the atomic lattice and the position of the fringe maxima and minima. Complete dynamical many-beam image simulations of the different interface models are presented for various values of defocus and sample thickness. The simulations indicate the most favourable imaging conditions for distinguishing between the different models. The influence of thermal atomic motion and inelastic scattering effects on the image is investigated. Experimental HREM images are presented of both A-type (fully aligned) and B-type (twinned) CoSi2/Si(111) interfaces. Careful comparison with simulated images reveals that at the A-type interface the Co atoms are coordinated by seven Si atoms, while at the B-type interface the Co atoms are eightfold coordinated. © 1990 Taylor & Francis Group, LLC.