Two-dimensional imaging of surface morphology by energy-analyzed secondary electrons and Auger electron spectroscopy for stepped Si(111) surfaces

Abstract

We have experimentally investigated two-dimensional imaging of stepped Si surfaces by energy-analyzed electrons and Auger electron spectra from atomically flat surfaces. A stepped Si(111) surface was prepared by direct-current heating to around 1250 °C in ultrahigh vacuum. The stepped surface consisted of atomically flat terraces and step bands where atomic steps bunched in the height of about 5 nm. We found that the stepped structure could be imaged by using only the energy-analyzed secondary electrons (SEs) when the intensity was defined as the difference between the peak height and the background intensity. The image from the energy-analyzed SEs was in good agreement with the conventional SEM image obtained with non-energy-analyzed SEs. The electron-emission spectrum obtained in the direct mode included only characteristic Auger peaks of silicon SE peak. It is found that the electron-emission spectrum obtained from the atomically flat Si(111) terrace has relatively higher background than that from a sputter-cleaned Si surface. Also, it is revealed that the fine structure exists at 2.2 eV in the SE peak.