Scanning tunneling microscopy of rough surfaces

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Abstract
When the high resolution capability of scanning tunneling microscopy(STM) is coupled with digital data acquisition, it is possible to get quantitative information on surface texture. This capability has been used for surface roughnessmeasurement, and searching for fractal behavior. The peak altitude method of measurement of surface roughness is illustrated for evaporated goldfilms and the dependence of roughness on deposition temperature and annealing time is described. By using algorithms for scale dependent measurement of surface area, the existence of fractal morphology is investigated. This method is used to contrast the behavior of the fracture of steel vs epoxy resin. The results on goldfilms show a clear trend for which the roughness, as well as the experimental deviance of the roughness, is found to be minimal for evaporation at 300 °C. The limitations of STM for roughnessmeasurement are discussed. The steel fracturesurfaces were similar on length scales studied, but were highly variable over the studied surfaces. A fractal dimension was determined, and this value was compared to fractal dimensions determined previously by lower‐resolution techniques. On the other hand, the resin fracture did not fit well with the expected behavior of either a geometric surface, or that of a self‐similar surface.

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