Inserting an atomic trap for directional dopant migration in core/multi-shell quantum dots

Diffusion of atoms or ions in solid crystalline lattice is crucial in many areas of solid-state technology. However, controlling ion diffusion and migration is challenging in nanoscale lattices. In this work, we intentionally insert a CdZnS alloyed interface layer, with small cationic size mismatch with Mn(ii) dopant ions, as an atomic trap to facilitate directional (outward and inward) dopant migration inside core/multi-shell quantum dots (QDs) to reduce the strain from the larger cationic mismatch between dopants and host sites. Furthermore, it was found that the initial doping site/environment is critical for efficient dopant trapping and migration. Specifically, a larger Cd(ii) substitutional site (92 pm) for the Mn(ii) dopant (80 pm), with larger local lattice distortion, allows for efficient atomic trapping and dopant migration; while Mn(ii) dopant ions can be very stable with no significant migration when occupying a smaller Zn(ii) substitutional site (74 pm). Density functional theory calculations revealed a higher energy barrier for a Mn(ii) dopant hopping from the smaller Zn substitutional tetrahedral (Td) site as compared to a larger Cd substitutional Td site. The controlled dopant migration by atomic trapping inside QDs provides a new way to fine tune the properties of doped nanomaterials. Directional Mn dopant migration (outward/inward) was achieved by inserting a CdZnS atomic trap with a small size mismatch with dopants in core/multi-shell QDs. A larger initial substitutional site allows for active trapping and dopant migration.

Automated summary

Diffusion and migration of atoms or ions in solid crystalline lattice play a crucial role in solid-state technology. However, it is challenging to control ion diffusion and migration in nanoscale lattices. In this study, an atomic trap consisting of a CdZnS alloyed interface layer was intentionally inserted to facilitate directional dopant migration inside core/multi-shell quantum dots (QDs). The research found that the initial doping site/environment is crucial for efficient dopant trapping and migration. Density functional theory calculations revealed that the energy barrier of dopant hopping is higher when occupying a smaller substitutional site. This controlled dopant migration provides a new approach to fine-tune the properties of doped nanomaterials.