Surface Topography of Pyrolitic Carbons and of Au Thin Films by Scanning Tunneling Microscopy: Grain Boundaries and Surface Defects

摘要

We have shown using STM that Au thin films (approx. =10 nm) deposited on mica have a smoothly rolling hill structure that can be flattened to the atomic level by mild (250 deg C) annealing. This treatment resulted in a film surface with extended regions of several hundred nm where the only departures from the atomic surface plane are isolated steps of monoatomic height. Residual bumps and trenches are the only imperfections on the scale of nm. The surface topography of pyrolitic carbons prepared at various temperatures revealed crystallite sizes and orientation in approximate agreement with x-ray data. Grain boundaries between the various crystallites were examined and revealed that the extent of the transition region varies from sharp atomic dimensions to several tens of nm wide. Defects in the form of steps and localized points are observed in the center of the otherwise atomically smooth crystallite surfaces. Atomically resolved images of the crystallite surface indicate a periodicity consistent with the missing atom observations on graphite. (ERA citation 12:031113)