Noncontact Atomic Force Microscopy - Yale School of Engineering ...

P.I-02
Force Map of Atomic Force Microscopy on Si(111)-(5x5)-DAS Surface
Akira Masago and Masaru Tsukada
WPI-AIMR, Tohoku University, 2-1-1 Katahira, Aoba, Sendai, 980-8577 Japan
Recently, lateral force mapping has been performed by atomic force microscopy (AFM)
on the Si(111)-(7x7)-(Dimer-Adatom-Stacking fault (DAS)) surface, as well as potential
and vertical force mapping. We believe that they provide us with useful information for
atomic identification and manipulation. In this study, we simulated force maps along the
long diagonal direction of the unit cell of the Si(111)-(5x5)-DAS surface using the
density-functional based tight-binding (DFTB) calculation. As a result, we obtained force
maps shown in Fig. 1, using a Si4H9 cluster tip. In the vertical force map, the small peaks
located at the rest atoms (Rs) as well as the large peaks at the adatoms (Ad). Moreover,
the plateaus also exist at bridge site (Br) of the adatoms out of the scan trajectory. In the
lateral force maps, we can see paired peaks located at the adatoms and rest atoms. These
characters must be related with the atomic configuration of the tip apex. In our
presentation, we will talk about the relation between remarkable characters that present
on the force maps and various configurations of the tip apex.
Figure 1: Vertical and lateral force maps when the tip scans along a long diagonal line of a unit
cell of the Si(001)-(5x5)-DAS surface as well as side and top views of the surface. All circles
denote Si atoms, where open and fill circles denote adatoms and rest atoms, respectively. In
particular, open circles written in bold face are adatoms on the scan trajectory.
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