Spectroscopic Information in Scanning Tunneling Microscopy
During the last ten years, the Scanning Tunneling Microscope (STM) was proved to be a very powerful tool to obtain local structural information on metallic and semiconducting surfaces [4.1]. Many studies were devoted to the imaging of steps, roughness, reconstructions, or adsorbates of larger and larger complexity on these surfaces. Moreover, the spectroscopic mode of the STM, in which the tunneling current I is recorded as a function of the applied bias V, was shown to give information on the local electronic structure of the surfaces. In some cases, it allowed to discriminate the contributions of inequivalent atoms at the surface [4.2]. The I–V curves, or dlog I/d log V depending upon the authors, are usually interpreted in terms of the local density of states at the observed point of the surface. A rough one to one correspondence with ultra-violet photoemission spectra gave a qualitative experimental support to such a conjecture [4.3]. It is of course highly desirable to assess whether this correspondence may be put on quantitative grounds, so that finer and finer information could be extracted from spectroscopic data.
KeywordsScan Tunneling Microscope Tunneling Current Scan Tunneling Microscope Image Logarithmic Derivative Barrier Width
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