Surface-relaxation-induced giant corrugation on graphite (0001)

Soft graphite surface was atomically resolved by ultrasmall amplitude dynamic force microscopy operating at 5 MHz. The giant corrugation amplitude of up to 85 pm appeared due to local vertical deformations of the graphite surface. In simultaneous scanning tunneling microscopy and dynamic force microscopy, all of the symmetric C atoms were resolved with the conservative interaction in the repulsive regime. Additionally, the dissipative interaction showed a large difference of asymmetric $\alpha$ and $\beta$ site C atoms, arising from the different mechanical properties. The low stiffness of the graphite surface played a crucial role in the observations at room temperature.

Figure 1

DFM topographies of the graphite surface obtained with the second resonance mode. (a) $100\times 100{\text{nm}}^2$, $f_{2\text{nd}}=1.765551\text{MHz}$, $Q_{2\text{nd}}=8211$, $A_{2\text{nd}}=650\text{pm}$, $\Delta f_{2\text{nd}}=-30\text{Hz}$, and the applied bias voltage $V_{\text{bias}}=0\text{V}$. (b) $3\times 3{\text{nm}}^2$, $f_{2\text{nd}}=1.737255\text{MHz}$, $Q_{2\text{nd}}=8156$, $A_{2\text{nd}}=220\text{pm}$, $\Delta f_{2\text{nd}}=-28\text{Hz}$, and $V_{\text{bias}}=0.2\text{V}$.

Figure 2

(Color online) DFM topographies obtained with the third resonance mode. (a) $\Delta f_{3\text{rd}}=-13\text{Hz}$, $A_{3\text{rd}}=120\text{pm}$, $V_{\text{bias}}=0.2\text{V}$, and $11\times 11{\text{nm}}^2$. (b) $f_{3\text{rd}}=-6\text{Hz}$. (c) $f_{3\text{rd}}=+52\text{Hz}$. [(d) and (e)] Line profiles along $A\text{−}{A}^{\prime }$ in (b) and (c), respectively. $A_{3\text{rd}}=210\text{pm}$, $V_{\text{bias}}=0\text{V}$, and $1.2\times 1.2{\text{nm}}^2$. The $\alpha$ site (yellow). The $\beta$ site (blue). $f_{3\text{rd}}=4.790437\text{MHz}$ and $Q_{3\text{rd}}=10085$.

Figure 3

Observed corrugation amplitude as a function of the frequency shift.

Figure 4

(Color online) (a) Conservative and (b) dissipative interaction maps and (c) STM topography. [(d)–(f)] Line profiles along $A\text{−}{A}^{\prime }$ in (a), (b), and (c), respectively. Image size: $0.71\times 1.2{\text{nm}}^2$, $V_{\text{bias}}=-0.8\text{V}$, and ${\overline{I}}_t=400\text{pA}$. The cantilever was the same as in Fig. 1b. $A_{2\text{nd}}^{\prime }=50\text{pm}$. The $\alpha$ site (yellow). The $\beta$ site (blue).