| Summary: | 碩士 === 國立交通大學 === 材料科學與工程系所 === 95 === Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) are employed in this thesis to study the surface topography and the Gundlach Oscillation on metal surface. The separations of standing wave states between the films and substrates vary with the characteristics of the surface. Constant energy separations between the film and substrates exhibit in uniform and various thin film systems. We proposed a model to explain the energy separation, and it is considered as the work function difference between the film and substrates. According to our result, the energy separations at higher bias are field-independent.
Our results also show that the intensity of Gundlach Oscillation varies with distinct structures. Higher intensity of Gundlach Oscillation occurs accompanied with lower transmissivity. However for the same material, the Gundlach oscillation intensities of distinct regions are conserved during Z-V measurement. It shows that different structures response distinctly at the energy of standing wave states. Observing reconstructed Au(111) surface with Z-V measurement, the resolution is better than 1.1nm even when the tip-sample displacement is large as 60Å. This technique is quite applicable in observing soft materials as carbon nanotubes or DNA. Generally soft materials tend to be dragged by the tip since the distance between the tip and sample is less than 10Å. Such dragging can be avoided if the scanning is operated with several nanometers as tip-sample distance.
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