Phosphorus Oxidation\nControls Epitaxial Shell Growth\nin InP/ZnSe Quantum Dots

InP/ZnSe/ZnS core/shell/shell quantum dots are the most\ninvestigated\nquantum dot material for commercial applications involving visible\nlight emission. The inner InP/ZnSe interface is complex since it is\nnot charge balanced, and the InP surface is prone to oxidation. The\nrole of oxidative defects at this interface has remained a topic of\ndebate, with conflicting reports of both detrimental and beneficial\neffects on the quantum dot properties. In this study we probe the\nstructure of the InP/ZnSe interface at the atomic level using <sup>31</sup>P, <sup>77</sup>Se and <sup>17</sup>O ssNMR and HAADF-STEM.\nWe observe clear differences in Se NMR spectra and crystal orientation\nof core and shell when the InP/ZnSe is oxidized on purpose. High levels\nof interface oxidation result in an amorphous phosphate layer at the\ninterface, which inhibits epitaxial growth of the ZnSe shell.