Quantum well states in ultrathin Bi films: Angle-resolved photoemission spectroscopy and first-principles calculations study
Quantum well states in ultrathin Bi films: Angle-resolved photoemission spectroscopy and first-principles calculations study
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DOI：
10.1103/physrevb.75.035422
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发表时间：
2007-01-01
影响因子：
3.7
通讯作者：
Hasegawa, S.
中科院分区：
文献类型：
--
作者：
Hirahara, T.;Nagao, T.;Hasegawa, S.
通过角分辨光电子能谱和第一原理计算，研究了在厚度达数十纳米的 Si(111)-7 x 7 上生长的超薄 Bi(001) 薄膜中的量子阱态 (QWS)。我们在 k 空间的不同点观察了 QWS；位于棒上 (Gamma) 附近的那些非常难以区分，而棒上非正常发射 (M) 处的 QWS 峰则清晰可见，并且由于沿着 L-X 方向的块体 Bi 费米能级附近的鞍点状能带色散而显示出高度各向异性特征。通过对独立 Bi 板的从头计算，可以很好地再现 QWS 的特征。将相移累积模型的标准方法应用于QWS，首次通过实验获得了有限平行动量下垂直于表面的体能带色散。详细讨论了薄膜界面处的相移。 QWS 对费米能级附近的电子结构几乎没有贡献，这表明几个原子层厚度的薄膜的宏观物理性质可能由高金属表面态决定。
Quantum well states (QWSs) in ultrathin Bi(001) films grown on Si(111)-7 x 7 with thicknesses up to several tens of nanometers were studied by angle-resolved photoemission spectroscopy and first-principles calculations. We observed QWSs at various points in k-space; those located near (Gamma) over bar are very difficult to distinguish while the QWS peaks at off-normal emission (M) over bar are clearly resolved and show highly anisotropic features due to the saddle-point-like band dispersion near the Fermi level of bulk Bi along the L-X direction. The features of the QWSs are well-reproduced by ab initio calculations for free-standing Bi slabs. The standard method of the phase-shift accumulation model is applied to the QWSs and the bulk band dispersion perpendicular to the surface at finite parallel momentum is experimentally obtained for the first time. The phase shifts at the film interfaces are discussed in detail. The QWSs have little contribution to the electronic structure near the Fermi level and this suggests that the macroscopic physical properties of the films in the thickness of several atomic layers are likely determined by the highly metallic surface states.