Contrasted electronic properties of Sn-adatom-based ( 3 × 3 ) R 30 ° reconstructions on Si(111)
Contrasted electronic properties of Sn-adatom-based ( 3 × 3 ) R 30 ° reconstructions on Si(111)
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Si(111) 上基于 Sn 吸附原子的 ( 3 × 3 ) R 30 ° 重建的电子特性对比
DOI：
10.1103/physrevb.64.115407
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发表时间：
2001
影响因子：
3.7
通讯作者：
J. Themlin
中科院分区：
文献类型：
--
作者：
A. Charrier;R. Pérez;F. Thibaudau;J. Debever;J. Ortega;F. Flores;J. Themlin
我们研究了二维固溶体${\mathrm{Si}}_{x}{\mathrm{Sn}}_{1\ensuremath{-}x}/\mathrm{Si}(111)\ensuremath{-}(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$在室温下的电子结构，特别强调了空态，使用全局$[{k}_{//}$ -分辨逆光电发射光谱（KRIPES）和局部探针（扫描隧道显微镜和光谱，STM和STS），以及DFT-LDA计算。该吸附原子覆盖层具有$(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$对称性，随着sn -吸附原子浓度的增加而急剧演变，包括半导体到金属的转变。${\mathrm{Si}}_{0.5}{\mathrm{Sn}}_{0.5}/\mathrm{Si}(111)\ensuremath{-}\sqrt{3}$或镶嵌相具有单一的空表面态，定位于${E}_{F}$和$\overline{\ensuremath{\Gamma}}.$之上的0.56 eV，总带宽为$\ensuremath{\approx}0.15 \mathrm{eV},$，这种定位于硅原子上的${\mathrm{sp}}_{z}$型状态不穿过${E}_{F}:$，镶嵌相具有半导体性质，带隙在0.3和0.5 eV之间。该相的特点是具有0.75 \AA{}的大波纹，且锡的附着原子高于硅的附着原子。在富锡极限${\mathrm{Si}}_{x}{\mathrm{Sn}}_{1\ensuremath{-}x}/\mathrm{Si}(111)\ensuremath{-}\sqrt{3}$和$xl~0.05,$中，我们沿着一个空态${U}_{1}^{\ensuremath{'}}$穿过大部分表面布里渊区，除了在$\overline{K}$点附近，它明显穿过费米能级。第二个空表面态${\mathrm{U}}_{2}^{\ensuremath{'}}$在${E}_{F}.$上方1.67 eV处被检测到，一旦充分考虑到${U}_{1}^{\ensuremath{'}}$的小带宽所暗示的相关效应，我们将动态波动模型框架内的KRIPES结果解释为源自底层$(3\ifmmode\times\else\texttimes\fi{}3)$结构。最后，根据两种极限情况解释了与中间Sn-adatom浓度有关的结果。
We have investigated the electronic structure of the two-dimensional solid solution ${\mathrm{Si}}_{x}{\mathrm{Sn}}_{1\ensuremath{-}x}/\mathrm{Si}(111)\ensuremath{-}(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$ at room temperature, with a particular emphasis on the empty states, using both global $[{k}_{//}$-resolved inverse photoemission spectroscopy (KRIPES)] and local probes (scanning tunneling microscopy and spectroscopy, STM and STS), as well as DFT-LDA calculations. This adatom overlayer with a $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$ symmetry shows drastic evolution with increasing Sn-adatom concentration, including a semiconductor to metal transition. The ${\mathrm{Si}}_{0.5}{\mathrm{Sn}}_{0.5}/\mathrm{Si}(111)\ensuremath{-}\sqrt{3}$ or mosaic phase has a single empty surface state localized at 0.56 eV above ${E}_{F}$ at $\overline{\ensuremath{\Gamma}}.$ With an overall bandwidth of $\ensuremath{\approx}0.15 \mathrm{eV},$ this ${\mathrm{sp}}_{z}$-type state localized on Si adatoms does not cross ${E}_{F}:$ the mosaic phase is semiconducting, with a bandgap between 0.3 and 0.5 eV. This phase is characterized by a large corrugation of 0.75 \AA{} with Sn adatoms higher than Si adatoms. In the Sn-rich limit ${\mathrm{Si}}_{x}{\mathrm{Sn}}_{1\ensuremath{-}x}/\mathrm{Si}(111)\ensuremath{-}\sqrt{3}$ with $xl~0.05,$ we follow an empty state ${U}_{1}^{\ensuremath{'}}$ throughout most of the surface Brillouin zone except near the $\overline{K}$ point where it clearly crosses the Fermi level. A second, empty surface state ${\mathrm{U}}_{2}^{\ensuremath{'}}$ is detected 1.67 eV above ${E}_{F}.$ Once correlation effects suggested by the small bandwidth of ${U}_{1}^{\ensuremath{'}}$ are adequately taken into account, we explain our KRIPES results in the framework of a dynamical fluctuations model as originating from an underlying $(3\ifmmode\times\else\texttimes\fi{}3)$ structure. Finally, results pertaining to intermediate Sn-adatom concentrations are interpreted in view of the two limiting cases.