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Raman spectroscopy of very small Cd 1−x Co x S quantum dots grown by a novel protocol: direct observation of acoustic‐optical phonon coupling
Author(s) -
Freitas Neto E. S.,
Silva A. C. A.,
Silva S. W.,
Morais P. C.,
Gómez J. A.,
Baffa O.,
Dantas N. O.
Publication year - 2013
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.4324
Subject(s) - raman spectroscopy , phonon , quantum dot , electron paramagnetic resonance , amorphous solid , condensed matter physics , materials science , ion , crystal (programming language) , molecular physics , analytical chemistry (journal) , crystallography , chemistry , nuclear magnetic resonance , optics , optoelectronics , physics , programming language , organic chemistry , chromatography , computer science
Glass‐embedded Cd 1−x Co x S quantum dots (QDs) with mean radius of R ≈ 1.70 nm were successfully synthesized by a novel protocol on the basis of the melting‐nucleation synthesis route and herein investigated by several experimental techniques. Incorporation of Co 2+ ions into the QD lattice was evidenced by X‐ray diffraction and magnetic force microscopy results. Optical absorption features with irregular spacing in the ligand field region confirmed that the majority of the incorporated Co 2+ ions are under influence of a low‐symmetry crystal field located near to the Cd 1−x Co x S QD surface. Electron paramagnetic resonance data confirmed the presence of Co 2+ ions in a highly inhomogeneous crystal field environment identified at the interface between the hosting glass matrix (amorphous) and the crystalline QD. The acoustic‐optical phonon coupling in the Cd 1−x Co x S QDs (x ≠ 0.000) was directly observed by Raman measurements, which have shown a high‐frequency shoulder of the longitudinal optical phonon peak. This effect is tuned by the size‐dependent sp‐d exchange interaction due to the magnetic doping, causing variations in the coupling between electrons and longitudinal optical phonon. Copyright © 2013 John Wiley & Sons, Ltd.