Internal Structure of InP/ZnS Nanocrystals Unraveled by High-Resolution Soft X-ray Photoelectron Spectroscopy

摘要

High-energy resolution photoelectron spectroscopy (Delta E < 200 meV) is used to investigate the internal structure of semiconductor quantum dots containing low 2-contrast elements. In InP/ZnS core/shell nanocrystals synthesized using a single-step procedure (core and shell precursors added at the same time), a homogeneously alloyed InPZnS core structure is evidenced by quantitative analysis of their In3d(5/2) spectra recorded at variable excitation energy. When using a two-step method (core InP nanocrystal synthesis followed by subsequent ZnS shell growth), XPS analysis reveals a graded core/shell interface. We demonstrate the existence of In-S and S-x-In-P1-x bonding states in both types of InP/ZnS nanocrystals, which allows a refined view on the underlying reaction mechanisms.