Figure 1

Force (in nN) as a function of distance (in nm) of the “silicon” AFM tip from the surface of a carbon SWNT of diameter $d=1.4\mathrm{nm}$. The $X$’s denote the experimental data, Ref. 1, and are given as a function of $D$, which has a zero set by an estimate of the short-range tip-SWNT repulsion. The results of the calculations are shown as a function of the distance $Z$ obtained from the distance $z$ of the tip from the SWNT axis using $Z=z-(d∕2)$. The arrows show the effect of a displacement of the origin of $D$ by $0.1\mathrm{nm}$. The van der Waals forces are calculated with $\gamma =0.1$. The open squares are for a pure silicon tip with $R=2\mathrm{nm}$ and the open circles are for $R=1.5\mathrm{nm}$. The filled symbols have the same shape, but the outer 1.0 $\left(0.5\right)\mathrm{nm}$ consists of $\mathrm{Si}{\mathrm{O}}_2$ for $R=2.0\left(1.5\right)\mathrm{nm}$, respectively. The dot-dash line represents the electrostatic force on a point charge $\mid e\mid$ at distance $Z$ from a grounded conducting cylinder of radius $d∕2$.Reuse & Permissions