Diluted magnetic semiconductors CdMnS and CdMnSe quantum dots (QDs) are successfully synthesized by reverse micelle method. The QDs are characterized by the high-resolution transmission electron microscopy (HRTEM), energy dispersion spectrometry (EDS), electron spin resonance (ESR), optical absorption and photoluminescence (PL) measurements. _{2 2 2}...[ Read more ]

Diluted magnetic semiconductors CdMnS and CdMnSe quantum dots (QDs) are successfully synthesized by reverse micelle method. The QDs are characterized by the high-resolution transmission electron microscopy (HRTEM), energy dispersion spectrometry (EDS), electron spin resonance (ESR), optical absorption and photoluminescence (PL) measurements.

For CdMnS QDs, two methods have been employed for the synthesis. One is using Na₂S as the sulfur source like what other researchers do, and the other is using H₂S as the sulfur source. The latter exhibits a systematic control of the dot size with the amount of H₂S incorporated. To our knowledge, this method has so far never been reported by others. HRTEM analysis shows that the CdMnS QDs synthesized with the two methods are both almost spherical in shape and defect free. The quantum confinement effect due to different dot sizes and bowing effect due to different Mn²⁺ contents are observed in the optical absorption spectra of these QDs. The PL spectra with different dot sizes and Mn²⁺ concentrations show a broad luminescence band, which is ascribed to emissions associated to Mn²⁺ and surface trap related states.

Similarly, the CdMnSe QDs are synthesized in reverse micelles with the dot sizes controlled by the water content. The optical properties of the QDs samples with various dot sizes and Mn²⁺ concentrations have been studied both in solution and thin film sample form at room temperature and low temperature, respectively. The temperature dependence and excitation power dependence of the CdMnSe QDs PL spectra show that the luminescence comes from the Mn²⁺ related emission combined with excitonic emission.

For both CdMnS and CdMnSe QDs, the ESR studies identified two Mn²⁺ sites. One is substituting the Cd²⁺ site and the other is located near the surface.