An applicability of scanning tunneling microscopy for surface electron spectroscopy

Electron energy loss and Auger electron spectra have been obtained for Si(1 1 1) covered with 0.02 bilayer Ge with a scanning tunneling microscope (STM) combined with an electron energy analyzer. The Ge islands with 5×5 and 7×7 reconstructions grown on the step and the domain boundaries of the Si(1 1 1)7×7 substrate are imaged with the STM. After STM imaging, the STM tip is retracted and the primary electron beam for these spectroscopies is field emitted from the tip of build-up [1 1 1]-oriented W, which has the most protruding point of the [1 1 1] apex. Several energy peaks are found, which are probably attributed to plasmon and to Auger electrons of Si LVV and Ge MVV. The origin of anomalous peak shift with decreasing separation between tip and sample is discussed.