Interplay between Cr Dopants and Vacancy Clustering in the Structural and Optical Properties of WSe2
Résumé
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 CrW-Vse 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).
Mots clés
- technology
- engineering and mathematics)
- Transition metals
- Transmission electron microscopy
- Vacancies
- Compressive strain
- Effective electrons
- Local phase transition
- Optical band gap energy
- Scanning transmission electron microscopy
- Structural and optical properties
- Transition metal dichalcogenides
- Vacancy clustering
- Doping (additives)
- STEM (science
- Selenium compounds
- Scanning electron microscopy
- Optical properties
- Optical lattices
- High resolution transmission electron microscopy
- Energy dissipation
- Electrons
- Electron scattering
- Electron energy loss spectroscopy
- Electron energy levels
- Density functional theory
- Defects
- Binding energy