Phosphorus Oxidation Controls Epitaxial Shell Growth in InP/ZnSe Quantum Dots
Reinout F. Ubbink (TU Delft - ChemE/Opto-electronic Materials)
Tom Speelman (Radboud Universiteit Nijmegen)
Daniel Arenas Esteban (Universiteit Antwerpen)
M. van Leeuwen (Student TU Delft)
M. Stam (TU Delft - ChemE/Opto-electronic Materials)
Sara Bals (Universiteit Antwerpen)
Gilles A. De Wijs (Radboud Universiteit Nijmegen)
Ernst R.H. van Eck (Radboud Universiteit Nijmegen)
Arjan J. Houtepen (TU Delft - ChemE/Opto-electronic Materials)
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Abstract
InP/ZnSe/ZnS core/shell/shell quantum dots are the most investigated quantum dot material for commercial applications involving visible light emission. The inner InP/ZnSe interface is complex since it is not charge balanced, and the InP surface is prone to oxidation. The role of oxidative defects at this interface has remained a topic of debate, with conflicting reports of both detrimental and beneficial effects on the quantum dot properties. In this study we probe the structure of the InP/ZnSe interface at the atomic level using 31P, 77Se and 17O ssNMR and HAADF-STEM. We observe clear differences in Se NMR spectra and crystal orientation of core and shell when the InP/ZnSe is oxidized on purpose. High levels of interface oxidation result in an amorphous phosphate layer at the interface, which inhibits epitaxial growth of the ZnSe shell.
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