Figure 1

(Color online) (a) STM image of the graphite surface with a point vacancy defect at 5.4 K ($5.0\times 5.0{\text{nm}}^2$, sample bias $V_s=301\text{mV}$, and tunneling current $I_t=153\text{pA}$). The inset shows two-dimensional Fourier transform of the image, where the spots forming the inner hexagon represent the $\left(\sqrt{3}\times \sqrt{3}\right)R30°$ superstructure observed in the vicinity of the defect. The STS spectra taken at the points A–D are represented at the right-hand side of the image. (b) Spatial distribution of the STS peak intensity observed around the defect, where the $dI/dV$ peak intensity in STS spectrum is plotted by color solid circle. (c) Schematic image of the point vacancy defect on graphite. Three zigzag edges at the defect are represented by solid zigzag lines. The size of the solid circle represents the intensity of the local density of states (edge states). The arrows perpendicular to the zigzag edge represent the propagation direction of the edge states. [(d)–(i)] Space-resolved STS spectra (STS map) taken at the line in the corresponding STM image. In each case, STS results from left to right at line are shown as STS map from left to right.Reuse & Permissions

Figure 2

(Color online) (a) STM image obtained during the STS measurements at 5.4 K ($0.9\times 2.8{\text{nm}}^2$, $V_s=300\text{mV}$, and $I_t=150\text{pA}$). [(b) and (c)] Peak intensity and energy of the $dI/dV$ peak in the STS spectrum along ${\text{AA}}^{\prime }$ in STM image $a$, respectively. The solid curve is a guide. “$d$” represents the distance to the nearest-neighboring $\beta$-carbon atoms, 0.25 nm. (d) Space-resolved STS spectra along ${\text{A-A}}^{\prime }$ in $a$. (e) The definitions of the peak intensity and energy of the STS spectrum are represented by red (dark gray) and black arrows, respectively.Reuse & Permissions

Figure 3

(Color online) (a) STM image obtained during STS measurements at 5.3 K ($2.0\times 3.5{\text{nm}}^2$, $V_s=150\text{mV}$, and $I_t=150\text{pA}$). [(b) and (c)[ Peak intensity and energy of the $dI/dV$ peak in the STS spectrum along ${\text{AA}}^{\prime }$ in $a$, respectively. The solid curve is a guide. “$d$” represents the distance to the nearest-neighboring $\beta$-carbon atoms, 0.25 nm. (d) Space-resolved STS spectra along ${\text{A-A}}^{\prime }$ in $a$. (e) The definitions of the peak intensity and energy of the STS spectrum are represented by red (dark gray) and black arrows, respectively.Reuse & Permissions

Figure 4

(Color online) (a) STM image obtained during STS measurements at 5.3 K ($10.0\times 10.0{\text{nm}}^2$, $V_s=600\text{mV}$, and $I_t=150\text{pA}$). (b) STS results measured at the position 11 in $a$ with different tip-sample distances; (the results at the set points determined by $V_s=600\text{mV}$ and $V_s=500\text{mV}$ are shown). (c) Peak energy of the $dI/dV$ peak in the STS spectrum (arrow in $b$) at positions from 1 to 16 in $a$ at the tip-sample distance determined by the conditions of $V_s=600\text{mV}$ and $I_t=150\text{pA}$. (d) The same with $c$ except for the measurement condition of the tip-sample distance ($V_s=500\text{mV}$ and $I_t=150\text{pA}$).Reuse & Permissions