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Interplay Between Cr Dopants and Vacancy Clustering in the Structural and Optical Properties of WSe2

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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 STEM microscopy combined with EEL 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 CrW—Vse complex obtained by in DFT 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 suffers a compressive strain, resulting in an isotropic lattice contraction and in an anisotropic optical bandgap energy shift (25 meV in-plane and 80 meV out-of-plane).


C-H. Ho, W-H. Chen, K.K. Tiong, K-Y. Lee, A. Gloter, A. Zobelli, O. Stephan, and L. H. G. Tizei, ACS nano (2017)

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