Scanning tunneling microscopy and spectroscopy of the electronic local density of states of graphite surfaces near monoatomic step edges
Scanning tunneling microscopy and spectroscopy of the electronic local density of states of graphite surfaces near monoatomic step edges
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DOI：
10.1103/physrevb.73.085421
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发表时间：
2006-02-01
影响因子：
3.7
通讯作者：
Fukuyama, H
中科院分区：
文献类型：
--
作者：
Niimi, Y;Matsui, T;Fukuyama, H
我们运用扫描隧道显微镜（STM）和扫描隧道谱（STS）技术，测量了由锯齿形或扶手椅形边缘构成的单原子台阶边缘附近石墨表面的电子局域态密度（LDOS）。扫描隧道显微镜数据显示，在距离这两种边缘3 - 4纳米的长度范围内，（√3×√3）R30°和蜂窝状超结构共存。通过与密度泛函导出的非正交紧束缚计算结果进行对比，我们发现这种共存现象是由于石墨表面两种类型的边缘存在轻微混合。在扫描隧道谱测量中，在锯齿形边缘附近，于-100至 -20毫伏的负偏压下观察到局域态密度出现一个明显的峰，而在扶手椅形边缘附近未观察到这样的峰。我们得出结论，该峰对应于藤田[《日本物理学会志》65卷，1920页（1996年）]利用石墨烯带的紧束缚模型从理论上预测的石墨“边缘态”。我们针对不同边缘终止情况进行的第一性原理计算也证实了仅在锯齿形边缘存在边缘态。
We measured the electronic local density of states (LDOS) of graphite surfaces near monoatomic step edges, which consist of either the zigzag or armchair edge, with the scanning tunneling microscopy (STM) and spectroscopy (STS) techniques. The STM data reveal that the (root 3 x root 3) R30 degrees and honeycomb superstructures coexist over a length scale of 3-4 nm from both the edges. By comparing with density-functional derived nonorthogonal tight-binding calculations, we show that the coexistence is due to a slight admixing of the two types of edges at the graphite surfaces. In the STS measurements, a clear peak in the LDOS at negative bias voltages from -100 to -20 mV was observed near the zigzag edges, while such a peak was not observed near the armchair edges. We concluded that this peak corresponds to the graphite "edge state" theoretically predicted by Fujita [J. Phys. Soc. Jpn. 65, 1920 (1996)] with a tight-binding model for graphene ribbons. The existence of the edge state only at the zigzag type edge was also confirmed by our first-principles calculations with different edge terminations.