The direct imaging of the surface structure of thin crystalline films in the conventional transmission electron microscope (CTEM) requires resolution of a few angstroms both laterally and perpendicular to the atomic surface layers. Although the lateral resolution was not achieved, dark-field images of the forbidden reflections from (111) Au films could be employed to image lateral areas ∼500Å diameter. The first atomic level resolution pictures of the Au surface of (001) films were reported by Krakow and Ast. Here optical diffractograms revealed the presence of the forbidden surface reflections due to partially filled bulk lattice unit cells corresponding to a surface lattice periodicity of ∼2.86Å. Subsequently, improved electron micrographs were obtained at incident beam energies of lOOkV and at ImeV where in the latter case the microscope resolution was better than 2Å3. Several diffraction experiments were also performed to understand the nature of the surface structure of (001)Au. In this study models of a “single” (001)Au surface were constructed and computations performed to demonstrate the types of images attainable at different resolution levels and under different microscope imaging conditions.
Influence of Atomic Surface Structure on the Activity of Ag for the Electrochemical Reduction of CO2 to CO
