Surface electronic structures of Ca-induced reconstructions on Si(111)
Surface electronic structures of Ca-induced reconstructions on Si(111)
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Si(111) 上 Ca 诱导重建的表面电子结构
DOI：
10.1103/physrevb.68.245312
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发表时间：
2003
影响因子：
3.7
通讯作者：
H. Yeom
中科院分区：
文献类型：
--
作者：
Y. Kim;J. Kim;H. Lee;Y. Kim;H. Yeom
在Si（111）表面上吸附Ca诱导的单畴3 × 2和2 × I表面上进行了角分辨光电子能谱实验。对于3 X 2表面，我们确定了三个完全占据的表面状态内的Si体带隙与清晰的色散为0.3-0.6 eV。这些表面态带类似于Ba诱导的类似3×2相所观察到的带，并且与同一衬底上Li的3 × I相的理论计算大致一致。这一结果通常支持碱土金属吸附物诱导的3×2表面的蜂窝链式通道模型，其中碱金属将共同的Si最顶层（“主体”）重构为3×1表面。此外，我们还观察到表面态色散具有明显的×2对称性，这使得3×2相的表面能带结构与主体3×I重构的表面能带结构不同.在电子衍射中也很清楚的表观×2周期性归因于Ca吸附原子沿Si沟道沿着交替占据T4位，覆盖率为1/6 ML。在较高覆盖率下形成2×I重构时，在体带隙区只观察到一个表面态，结合能为1.1- 1.5eV。这种状态在链（×1）方向上表现出较大的沿着色散，这与裸Si（111）2 X I表面π键Seiwatz链结构的理论预测相一致.这一结果支持了最近提出的2×1表面的结构模型，即一维Ca链夹在π-honded Si链之间.从目前的观测结果可以推断，具有碱土金属吸附物的Si表面相的表面电子能带结构在很大程度上严格地由Si最顶层本身的重构决定。
Angle-resolved photoemission experiment was performed on the single-domain 3 X 2 and 2 X I surfaces induced by Ca adsorption on a Si(111) surface. For the 3 X 2 surface, we identify three fully occupied surface states within the Si bulk-band gap with clear dispersions of 0.3-0.6 eV. These surface-state bands resemble those observed for the similar 3×2 phase induced by Ba and are roughly consistent with the theoretical calculation for the 3 X I phase of Li on the same substrate. This result generally favors the honeycomb-chained channel model for the 3×2 surface induced by alkali-earth adsorbates with a common Si topmost layer ("host") reconstruction to the 3×1 surface by alkali metals. In addition, we observe a rather obvious ×2 symmetry in the surface-state dispersions, which differentiates the surface band structure of the 3×2 phase from that of the host 3×I reconstruction. The apparent ×2 periodicity, which is also clear in electron diffraction, is attributed to the alternating occupation of the T4 sites along the Si channels by Ca adatoms with a coverage of l/6 ML. In case of the 2×I reconstruction formed at a higher coverage, we observe only one surface state within the bulk-band-gap region at a binding energy of 1.1-1.5 eV. This state exhibits a larger dispersion along the chain (×1) direction, which agrees reasonably with the theoretical prediction for the π-bonded Seiwatz chain structure of the bare Si(111)2 X I surface. This result supports the recent structure model of the 2×1 surface with one-dimensional Ca chains in between π-honded Si chains. It is deduced from the present observations that the surface electronic band structures of the Si surface phases with alkali-earth adsorbates are largely and rigidly determined by the reconstruction of the Si topmost layer itself.