Raman spectroscopy of very small Cd sub(1-x)Co sub(x)S quantum dots grown by a novel protocol: direct observation of acoustic-optical phonon coupling

Glass-embedded Cd sub(1-x)Co sub(x)S quantum dots (QDs) with mean radius of R approximately 1.70nm 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 super(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 super(2+) ions are under influence of a low-symmetry crystal field located near to the Cd sub(1-x)Co sub(x)S QD surface. Electron paramagnetic resonance data confirmed the presence of Co super(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 sub(1-x)Co sub(x)S QDs (x[ne]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 [copy 2013 John Wiley & Sons, Ltd. An important step towards the development of diluted magnetic semiconductor nanostructures was presented by describing a new protocol to grow glass-embedded Cd sub(1-x)Co sub(x)S quantum dots. Direct observation of the acoustic-optical phonon coupling in these quantum dots was evidenced by a high-frequency shoulder of the longitudinal optical phonon peak in the Raman spectra. 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 phonons.