Phosphorus Oxidation Controls Epitaxial Shell Growth in InP/ZnSe Quantum Dots

Area of Science:

• Materials Science
• Nanotechnology
• Quantum Dot Research

Background:

• Indium phosphide/zinc selenide/zinc sulfide (InP/ZnSe/ZnS) core/shell/shell quantum dots are key for visible light emission applications.
• The InP/ZnSe interface presents challenges due to charge imbalance and InP oxidation, with debated effects of defects.

Purpose of the Study:

• To elucidate the atomic-level structure of the InP/ZnSe interface.
• To understand the role of oxidation and defects on quantum dot properties.

Main Methods:

• Utilized solid-state nuclear magnetic resonance (ssNMR) spectroscopy (³¹P, ⁷⁷Se, ¹⁷O).
• Employed high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).

Main Results:

• Observed distinct changes in Se NMR spectra and crystal orientation upon intentional oxidation.
• Identified high levels of interface oxidation leading to an amorphous phosphate layer.
• Demonstrated that this phosphate layer inhibits the epitaxial growth of the ZnSe shell.

Conclusions:

• Interface oxidation significantly alters the InP/ZnSe quantum dot structure.
• Amorphous phosphate layer formation due to oxidation is detrimental to shell epitaxy and quantum dot performance.