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

Submitted by ltizei on Wed, 2017-11-01 05:41
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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)

Point Defects in h-BN as efficient UV quantum emitters

Submitted by eels on Thu, 2017-01-05 16:18
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Single photons sources (SPS) play a central role in the experimental foundation of quantum computing. Currently, there is a large scientific effort in identifying new bright and stable single-photon emission sources, with the aim of extending the spectral range achievable by quantum emitters. In the last years low dimensional layered semiconductors appeared as new promising optical materials and low energy SPS have been identified in transition metal dichalcogenides. In this work, thanks to a newly developed optical set-up integrated in a scanning transmission electron microscope, we have identified a new very bright UV single photon emitter in hexagonal boron nitride. Read more »

Publications

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Cavalier, M., Walls, M., Lisiecki, I. & Pileni, M.P. How Can the Nanocrystallinity of 7 nm Spherical Co Nanoparticles Dispersed in Solution Be Improved?. Langmuir 27, 5014–5020 (2011).
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