Direct surface imaging in small metal particles

Atomic-level information about the surfaces of small metal particles has been recorded directly in recent observations with a 600-kV high-resolution electron microscope. Here, we have studied small polycrystalline particles of silver and gold tilted to bring their surfaces parallel to the electron beam. However, unlike previous workers using this normal reflection electron microscopy (REM) configuration, we have used conventional bright field axial imaging thereby considerably facilitating image interpretation. As well as clean, sharp surface images, morphological details of catalytic significance, such as the distribution of surface steps, particle facetting and the nature of surface reconstructions, have been obtained. Moreover, detailed computer simulations confirmed that the electron micrographs can be interpreted in terms of atomic columns and, in particular, established that some micrographs showed, for the first time in a transmission electron microscope (TEM), direct atomic-scale imaging of a reconstructed metal surface.