Imaging of chemical reactivity and buckled dimers on Si 100/2=1 reconstructed surface with noncontact AFM

We have investigated the force interactions between the Si tip and the Si 100.2=1 reconstructed surface in the noncontact atomic-force microscopy AFM.measurement. We observed two types of frequency shift curves without and with discontinuity, similar to the Si 111.7=7 surface. The image contrast changes drastically whether the frequency shift curve shows discontinuity or not. In the case of the frequency shift curves without discontinuity, the noncontact AFM images almost reflect the surface topography including dimers and adsorbates. In the case of the frequency shift curves with discontinuity, they reflect strongly the chemical reactivity of surface. Furthermore, in the case of the frequency shift curves without discontinuity, for the first time, the stabilize-buckling of dimers induced by a defect can be observed. This suggests that the force interactions during the noncontact AFM measurement hardly influence the surface dynamics. q1999 Elsevier Science B.V. All rights reserved.