Heterostructures of tellurium on NbSe2from sub-monolayer to few-layer films
Heterostructures of tellurium on NbSe2from sub-monolayer to few-layer films
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NbSe2 上碲的异质结构从亚单层到几层薄膜
DOI：
10.1039/c9nr09445h
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发表时间：
2020
期刊：
影响因子：
6.7
通讯作者：
Fu Ying-Shuang
中科院分区：
文献类型：
--
作者：
Xian Jing-Jing;Wang Cong;Zhang Zhi-Mo;Qin Le;Ji Wei;Chen Fang-Chu;Luo Xuan;Sun Yu-Ping;Zhang Wen-Hao;Fu Ying-Shuang
作为单元素体系，碲可以以层状形式稳定存在，具有有趣的多价特性，构成了二维家族的新成员。然而，目前对碲薄膜的生长和电子结构仍知之甚少。在这里，结合分子束外延、扫描隧道显微镜/光谱测量和密度泛函理论计算，我们报告了在 NbSe2 上生长的从亚单层到几层薄膜的碲的几何和电子结构。在亚单层覆盖范围内，我们获得了两种与 NbSe2 强耦合的吸附原子诱导的有序超结构。随着覆盖率的增加，少层碲薄膜呈现α相形式，在少层中呈现内部应变引起的波纹图案，在厚层中呈现块状，具有明显的边缘几何形状。 α-碲薄膜的带隙随着厚度的增加而减小，这与显着的带隙态有关。这些观察结果与 DFT 计算相证实，强调了 NbSe2 衬底在调节碲薄膜的结构和电子性能方面的重要作用。此外，碲吸附原子和碲薄膜之间的相互作用导致在新的单层之前进行√2×√2表面重建，这符合我们的理论计算。我们的工作阐明了碲薄膜在 NbSe2 上的动力学生长，并揭示了通过基板调制或表面装饰的电子特性的可调性。
As a single-elemental system, tellurium can exist stably in the form of layers with an intriguing multivalence character, which constructs a new member of the 2D family. However, the growth and electronic structure of tellurium films are still far from known at present. Here, combined with molecular beam epitaxy, scanning tunneling microscopy/spectroscopy measurements and density functional theory calculations, we report the geometric and electronic structures of tellurium grown on NbSe2 from sub-monolayer to few-layer films. At the sub-monolayer coverage, we obtain two types of adatom-induced ordered superstructures that are strongly coupled with NbSe2. With the increase in coverage, the few-layer tellurium films adopt the α-phase form, showing internal strain-induced ripple patterns in the few-layers and bulk-like in thick layers with distinct edge geometries. The band gap of α-tellurium films decreases with the increase in thickness, which is associated with notable in-gap states. These observations, corroborated with DFT calculations, emphasize the important role of the NbSe2 substrate in modulating the structural and electronic properties of tellurium films. Moreover, the interaction between tellurium adatoms and tellurium films leads to √2 × √2 surface reconstruction prior to a new monolayer, conforming to our theoretical calculations. Our work clarifies the kinetic growth of tellurium films on NbSe2 and reveals the tunability of electronic properties via substrate modulation or surface decoration.