Department of Physics, University of Texas at Austin, Austin, TX 78712, USA.
Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10617, Taiwan.
Sci Adv. 2017 Jan 6;3(1):e1601459. doi: 10.1126/sciadv.1601459. eCollection 2017 Jan.
By using direct growth, we create a rotationally aligned MoS/WSe hetero-bilayer as a designer van der Waals heterostructure. With rotational alignment, the lattice mismatch leads to a periodic variation of atomic registry between individual van der Waals layers, exhibiting a Moiré pattern with a well-defined periodicity. By combining scanning tunneling microscopy/spectroscopy, transmission electron microscopy, and first-principles calculations, we investigate interlayer coupling as a function of atomic registry. We quantitatively determine the influence of interlayer coupling on the electronic structure of the hetero-bilayer at different critical points. We show that the direct gap semiconductor concept is retained in the bilayer although the valence and conduction band edges are located at different layers. We further show that the local bandgap is periodically modulated in the - direction with an amplitude of ~0.15 eV, leading to the formation of a two-dimensional electronic superlattice.
通过直接生长，我们创建了一个旋转对准的 MoS/WSe 异质双层结构，作为一个设计的范德华异质结构。通过旋转对准，晶格失配导致范德华层之间的原子配位数周期性变化，表现出具有明确周期性的莫尔图案。通过结合扫描隧道显微镜/光谱学、透射电子显微镜和第一性原理计算，我们研究了原子配位数作为函数的层间耦合。我们定量地确定了层间耦合对不同临界点异质双层电子结构的影响。我们表明，尽管价带和导带边缘位于不同的层，但双层保留了直接带隙半导体的概念。我们进一步表明，局部能带隙在 - 方向上以约 0.15 eV 的幅度周期性调制，导致二维电子超晶格的形成。
