Simultaneous atomic force and scanning tunneling microscopy study of the Ge(111)-c(2x8) surface

In this article, the authors present the simultaneous noncontact atomic force microscopy and scanning tunneling microscopy measurement of the Ge(111)-c(2x8) surface using PtIr-coated Si cantilevers at room temperature. In both frequency shift and time-averaged tunneling current images at constant-height mode, each atom was clearly resolved. The image contrasts differ because the time-averaged tunneling current image is more directly coupled with local density of states than the frequency shift image. They demonstrate the measurement of the site-specific scanning tunneling spectroscopy (STS) spectra, which are in good agreement with typical STS measurements. Moreover, they demonstrate the simultaneous measurements of site-specific frequency shift and tunneling current as a function of tip-sample distance curves. On the Ge(111)-c(2x8) surface, tunneling current dropped at the near-contact region where a strong tip-sample interaction force is observed.(C) 2010 American Vacuum Society. [DOI: 10.1116/1.3305340]