Recognition of atomic species on hetero-surfaces by atom resolved tunneling spectroscopy

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The purpose of this study is to improve the reproducibility of scanning tunneling spectroscopy (STS) with an atomic resolution, which is called the atom resolved tunneling spectroscopy (ARTS). Since, in general, the electronic states of surfaces with various elements are locally settled by the characteristics of individual atoms on the surface, some changes in electronic states at each atomic site are possibly induced more or less. Consequently, it is expected that atomic species on sample surfaces with hybrid compositions can be recognized with an atomic resolution by prudent inspection with scanning tunneling microscopy (STM) /STS.The key point to achieve the recognition of surface atoms lies on the sharpness and electronic states at a tip apex, because the images obtained by the STS are altered by the tip conditions, easily and seriously.In this study, we have applied a build-up tip of [111] -oriented W for the ARTS of Si and Ge. The tip was treated under conditions of high temperat … More ure and high electric field. By the treatment the tip apex was surrounded by three {112} facets, and then the apex with the [111] orientation became sharper as a corner of the three facets. Furthermore, the treatment can remove impurity atoms not only from the tip apex, but also from the tip shank. Thus the sharpness and electronic states at tip apex can be reproduced by treatment. Then we have demonstrated the reproducibility of ARTS for Si (111) 7x7. The atomic change of the tip apex after the experiment was inspected by field emission microscope (FEM).Moreover, a new instrument combined with an atomic force microscope (AFM) and an electron energy analyzer has been developed to seek other possibilities of atom recognition on surfaces. The tip for AFM was treated to be cleaned and sharpened, and evaluated. By the energy analyzer, we have obtained backscattered electron energy spectra from the Si (111) surface exited by the field emission electron from the build-up tip, which showed bulk plasmon losses and an Auger peak of Si LVV.This results have demonstrated the availability of the combined new instrument for the atom recognition. Less