Performance Study On Scanning Probe Electron Energy Spectrometer Based On Toroidal Electron Energy Analyzer

As a very powerful tool in surface science, the Scanning Tunneling Microscope (STM) has been used intensively in topographic measurement and electronic-state-detection near the Fermi level of the solid surface. However, the principle of scanning probe technique prevents it from identifying the surface atoms. The combination of scanning probe technology and electron energy spectroscopy measurement technology is a promising way of identifying surface atoms at nanometer scale. In this way, the STM tip is used as the electron source in the field emission mode, and the elemental identification can be achieved by measuring the secondary electron energy spectroscopy. This thesis gives a description of the scanning probe electron energy spectrometer (SPEES) of our laboratory, which can be viewed as a hybrid between scanning field emission tip system and a toroidal electron energy analyzer (TEEA).Chapter 1 describes some basic concepts in the identification of surface atoms with scanning probes, the principle of the STM and recent progresses in the scanning probe electron spectrometers.Chapter 2 describes the whole setup of our present SPEES. The electron optics system of TEEA is introduced in detailed. Our SPEES which is based on TEEA can improve detection efficiency by about 2 orders of magnitude.In chapter 3, the performance of our spectrometer is studied systematically by using theory simulation as well as experimental methods. The influences of the axial non-symmetry of TEEA and barrel distortion of anode plate are investigated and a modification method is proposed.Meanwhile, we measure the LMM Auger spectrum of Ar gas, as well as the energy loss spectrum and the Auger spectrum of graphite.Chapter 4 tells of the measurement of the scanning probe energy loss spectrum for the Ag on HOPG surface by our SPEES. It is the first time for scanning probe technology that the elementary resolved spatial resolution has been obtained, although it is only about 5.0μm. This work demonstrates the potentially useful application for coupling a TEEA with an STM to achieve nano-scale elemental identification.