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Appearance of copper d 9 defect centres in wide‐gap CdSe nanoparticles: A high‐frequency EPR study
Author(s) -
Poolton N. R. J.,
Smith G. M.,
Riedi P. C.,
Allen J. W.,
Firth A. V.,
ColeHamilton D. J.,
McInnes E. J. L.
Publication year - 2005
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200440006
Subject(s) - electron paramagnetic resonance , luminescence , acceptor , paramagnetism , band gap , hyperfine structure , copper , materials science , nanoparticle , crystallography , molecular physics , atomic physics , chemistry , condensed matter physics , nuclear magnetic resonance , nanotechnology , physics , optoelectronics , metallurgy
When preparing CdSe nanoparticles in polybutadiene‐based polymer matrices, quantum confinement in the smaller particles leads to the usual increase in the band‐gap energy, with associated, well defined, band‐edge luminescence emission. However, for samples whose size is smaller than 3 nm, new broad luminescence features appear, with the simultaneous appearance of a new paramagnetic defect centre that has not previously been reported in the literature. This work concentrates on analyzing the electron paramagnetic resonance of the new defect, which is found to be located at a trigonally‐distorted tetrahedral site, with a spin S = 1/2 and g ‐values g || = 2.321 ± 0.006 and g ⊥ = 2.053 ± 0.006. With the attribution of very poorly resolved hyperfine interaction to a nucleus of spin I = 3/2, the identity of the defect is ascribed to copper in its d 9 state, which would be expected to act as a simple acceptor centre in CdSe. Conclusions are drawn to the effect that the defect normally resides within the valence band for bulk and large particles, only becoming apparent as a defect within the band‐gap as the energy increases above 2.6 eV in the smaller particles. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)