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Article Dans Une Revue Nanotechnology Année : 2019

Light-induced High-spin State in ZnO Nanoparticles

Résumé

The effects of white-light irradiation on ∼ 20 nm diameter ZnO nanoparticles are investigated by means of electron paramagnetic resonance, near liquid-nitrogen and liquid-helium temperatures. Under dark conditions, usual core-and surface-defects are detected, respectively at g = 1.960 and g = 2.003. Under white-light illumination, the core-defect signal intensity is strongly increased, which is to be correlated to the light-induced conductivity's augmentation. Beside, a four-lines structure appears, with the same gravity center as that of the surface defects. Simulations and intensity power-dependence measurements show that this four-line-structure is very likely to arise from a localized high spin S = 2, induced by light irradiation, and subjected to a weak axial anisotropy. At 85 K, this high-spin state can last several hours after the light-irradiation removal, probably due to highly spin-forbidden recombination process. The possible excited resonant complexes at the origin of this signal are discussed. Other light-induced S = 1/2-like centers are detected as well, which depends on the nanoparticles growth conditions.
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Dates et versions

hal-02321699 , version 1 (21-10-2019)

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Adrien Savoyant, M Rollo, M. Texier, R. Adam, S. Bernardini, et al.. Light-induced High-spin State in ZnO Nanoparticles. Nanotechnology, 2019, ⟨10.1088/1361-6528/ab57f1⟩. ⟨hal-02321699⟩
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