ODMR Measurements of CdSe\CdMnS Nanoplatelets

The current study invastigates the magneto-optical properties of an ensemble colloidal Nanoplatelets (NPs), doped with a few Mn⁺² ions (1%). Replacing a single atom of a host semiconductor nanocrystal with a functional dopant can introduce completely new properties potentially valuable for “solotronic” information-processing applications. The NPs consist of a CdSe core, covered by 8 monolayers (MLs) of CdMnS shell, adjusted to an appropriat band-gap by the size, and tuned to a quasi-type-II electronic alignment by variation of the core/shell-thickness ratio. The material design enables the appearance of the dopant excited states to lie nearly in resonance with the conduction band levels of the host semiconductor in order to create strong sp-d exchange interaction. The magneto-optical properties were investigated by probing the single exciton recombination emission of these NPs, using micro-photoluminescence (μPL) spectroscopy, obtaining an exchange split in the presence of an external magentic field (B₀). Well-resolved optically detected magnetic resonance (ODMR) peaks (Fiigure 2) are observed that can be related to the discrete spin projections of individual Mn²⁺ ions. Further more, a spin flip (magentic polaron) is examined by monitoring the mPL intensity under magnetic resonance conditions, m-PL magnetic resonance (mPL-MR) spectroscopy. These advanced measurements are the only way to reach spectral resolution of a sub-meV and control over a spin flip, essential for the detection of a spectroscopic fine structure generated by the exciton-Mn²⁺ interactions. The experimental results is supported by a theoretical model, based on the effective mass approximation of the NPs electronic states, perturbed by the relevant exchange interactions: electron-Mn⁺², hole- Mn⁺² and electron-hole, depending on the heterostructure design. This allows a calculation of the Mn⁺² g-factor together with the exciton-Mn⁺² coupling.