Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology , Taipei 106, Taiwan.
Graduate Institute of Electro-Optical Engineering and Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology , Taipei 106, Taiwan.
ACS Nano. 2017 Nov 28;11(11):11162-11168. doi: 10.1021/acsnano.7b05426. Epub 2017 Nov 7.
Here, we analyze the effect of Cr doping on WSe crystals. The topology and the chemistry of the doped samples have been investigated by atom-resolved scanning transmission electron microscopy combined with electron energy loss spectroscopy. Cr (measured to have formal valence 3+) occupies W sites (formal valence 4+), indicating a possible hole doping. However, single or double Se vacancies cluster near Cr atoms, leading to an effective electron doping. These defects organization can be explained by the strong binding energy of the Cr-V complex obtained by density functional theory calculations. In highly Cr-doped samples, a local phase transition from the 2H to the to 1T phase is observed, which has been previously reported for other electron-doped transition-metal dichalcogenides. Cr-doped crystals suffer a compressive strain, resulting in an isotropic lattice contraction and an anisotropic optical bandgap energy shift (25 meV in-plane and 80 meV out-of-plane).
在这里，我们分析了 Cr 掺杂对 WSe 晶体的影响。通过原子分辨扫描透射电子显微镜结合电子能量损失光谱研究了掺杂样品的拓扑结构和化学性质。Cr（测定具有形式价 3+）占据 W 位（形式价 4+），表明可能存在空穴掺杂。然而，单个或双 Se 空位在 Cr 原子附近聚集，导致有效电子掺杂。这些缺陷的组织可以通过密度泛函理论计算得到的 Cr-V 复合物的强结合能来解释。在高度掺杂的 Cr 样品中，观察到从 2H 到 1T 相的局部相变，这在以前的其他电子掺杂过渡金属二卤化物中已有报道。Cr 掺杂晶体受到压缩应变的影响，导致各向同性晶格收缩和各向异性光学带隙能量的变化（平面内 25 meV，平面外 80 meV）。
