Bi(111)的表面修饰及随后的费米密度增强
Surface Modification and Subsequent Fermi Density Enhancement of Bi(111)
AI总结：
结合实验与DFT计算，研究了Bi(111)表面二维缺陷及其诱导态，发现离子轰击产生的单层和双层台阶边缘显著增加了表面费米密度，且该状态在UHV下热力学稳定。
摘要：
引入Bi(111)表面的缺陷破坏了平移对称性，并在局部改变了表面态。我们提出了一项关于Bi(111)表面二维缺陷及其诱导态的理论与实验研究。在低温（110 K）下于超高真空（UHV）中解理的Bi晶体及其离子刻蚀后的表面，通过低能电子衍射（LEED）、X射线光电子能谱、紫外光电子能谱（UPS）以及扫描隧道显微镜（STM）与扫描隧道谱（STS）技术，结合密度泛函理论（DFT）计算进行了研究。解理Bi(111)的STS测量表明，与原子级平整的台地相比，常见的双层台阶边缘在费米能级附近的态密度（DOS）较低。在离子轰击后，Bi(111)表面在110 K和300 K下均表现出反常行为：LEED观察到了表面周期性，STM观察到了双层台阶边缘数量和能量不利的单层台阶的显著增加。据推测，新暴露的单层台阶和A型双层台阶边缘导致了表面费米密度的增加，UPS测量和Kohn-Sham态密度证实了这一点。这些态在UHV条件下似乎具有热力学稳定性。
英文摘要：
Defects introduced to the surface of Bi(111) break the translational symmetry and modify the surface states locally. We present a theoretical and experimental study of the 2D defects on the surface of Bi(111) and the states that they induce. Bi crystals cleaved in ultrahigh vacuum (UHV) at low temperature (110 K) and the resulting ion-etched surface are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) as well as spectroscopy (STS) techniques in combination with density functional theory (DFT) calculations. STS measurements of cleaved Bi(111) reveal that a commonly observed bilayer step edge has a lower density of states (DOS) around the Fermi level as compared to the atomic-flat terrace. Following ion bombardment, the Bi(111) surface reveals anomalous behavior at both 110 and 300 K: Surface periodicity is observed by LEED, and a significant increase in the number of bilayer step edges and energetically unfavorable monolayer steps is observed by STM. It is suggested that the newly exposed monolayer steps and the type A bilayer step edges result in an increase to the surface Fermi density as evidenced by UPS measurements and the Kohn-Sham DOS. These states appear to be thermodynamically stable under UHV conditions.
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