非接触原子間力顕微鏡によるSiとGe原子の識別

抄録

The intermixing can occur between deposited Ge and substrate Si atoms during the initial stage of the epitaxial growth of Ge on Si(111). Because of the miscibility of Ge and Si, it has been hampered to discriminate Ge and Si adatoms on the intermixed Ge/Si(111)-(7×7) surfaces by scanning tunneling microscopy. Here, we report successful identification of individual Ge and Si atoms by non-contact atomic force microscopy. By analyzing histograms of maximum attractive forces in force spectroscopy, we found that the more reactive tip we used the larger the separation of the peaks derived from Ge and Si became in the histograms. We demonstrate that the present method is also applicable to other reconstructed surfaces; Ge/Si(111)-(5×5). Although the adatoms in the topmost layer of Ge/Si(111)-(5×5) were dominantly occupied by Ge, a small amount of Si adatoms surely existed and were randomly distributed.