Phosphorus Oxidation Controls Epitaxial Shell Growth in InP/ZnSe Quantum Dots
Reinout F. Ubbink, Tom Speelman, Daniel Arenas Esteban, M. van Leeuwen, Maarten Stam, Sara Bals, G. A. de Wijs, Ernst R. H. van Eck, Arjan J. Houtepen
Abstract
High Resolution Image Download MS PowerPoint Slide 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 31 P, 77 Se and 17 O 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.