Figure 1

Experimental results: Conductance vs deformation. (a) Scheme of the experimental setup. (b) Pseudocolor map of $G(Z,V)$ measured on a 1.3 nm diameter SWNT. The vertical axis is the $Z$ piezoelectric displacement and the horizontal axis is the bias voltage. Black corresponds to zero and white to $27\mu \mathrm{A}/\mathrm{V}$. The diamondlike structures indicate conductance oscillations. (c) Plot of the conductances $G{|}_{0\mathrm{V}}$ (light gray) and $G{|}_{2\mathrm{V}}$ (dark gray) as a function of the cantilever normal force obtained from $F=-kZ$, where $k$ is the cantilever force constant ($3\mathrm{N}/\mathrm{m}$). (d) Conductance vs deformation plot obtained using the Hertz model for the data in (c).Reuse & Permissions

Figure 2

Extended contact region. (a) Atomistic scheme of the contact area between the tip and the nanotube. Inset: Schematic cross section of a tip deforming a SWNT, where we define the initial height $h$, the deformation $\delta$, and the effective height of the deformed nanotube $h_{\min }$. (b) Schematic drawing of the nanotube tip contact area divided in sections perpendicular to the tube axis. Gray curve (model a): $E(h)$ obtained from Ref. 5. Black curve (model b): $E(h)$ that leads to a good agreement with our experimental findings. According to our model and experimental setup, the measured $G$ is insensitive to the gap shape for $h<0.6\mathrm{nm}$. (c) Geometry of the tip-nanotube contact region. The area corresponding to the interface has been divided in $n$ sections perpendicular to the tube axis. Each of these sections has an assigned intrinsic resistance ($R_i$) and contact resistance ($R_{Ci}$) with the tip. Inset: Circuit equivalent to the experimental situation considered in the model. (d) Conductances vs $h_{\min }$ obtained with the models for the $E_{\mathrm{GAP}}(h)$ curves depicted in (b). A very good agreement with the experimental findings is found for the $E(h)$ plotted in black (model b).Reuse & Permissions

Figure 3

Phenomenological model for a metallic tip. (a),(b) Two fixed electrodes and an insulating tip setup. In (b), a gap has opened by tip deformation: The current flow is blocked by the opened gap. (c),(d) Fixed electrode and a conducting tip setup. (e) is for the same deformation as in (b), but the current flow is possible through the outer sections of the contact area.Reuse & Permissions