Here, we analyze the effect of Cr doping on WSe₂ 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_W–V_se 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).

中文翻译：

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WSe ₂的结构和光学性质中Cr掺杂剂和空位簇之间的相互作用

在这里，我们分析了Cr掺杂对WSe ₂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谱研究了掺杂样品的拓扑结构和化学性质。Cr（测得的形式化合价为3+）占据W位置（形式化合价为4+），表明可能存在空穴掺杂。然而，单或双Se空位聚集在Cr原子附近，导致有效的电子掺杂。Cr _W –V _se的强结合能可以解释这些缺陷的组织。通过密度泛函理论计算获得的复合物。在高Cr掺杂的样品中，观察到从2H相到1T相的局部相变，先前已报道过其他电子掺杂的过渡金属二卤化物。Cr掺杂的晶体受到压缩应变，导致各向同性的晶格收缩和各向异性的光学带隙能量移动（面内25 meV，面外80 meV）。