Identification of core/shell structure in Cd‐Zn‐Se QDs inside silicate glasses using 3D elemental distribution analysis

Abstract

Core-shell structure in Cd-Zn-Se quantum dots (QDs) precipitated in the silicate glass matrix by continuous wave laser (λ = 532 nm) were demonstrated using transmission electron microscopy (TEM) and local electrode atom probe (LEAP) tomography. TEM images of the QDs in glasses after 60 min of irradiation at 9 W/cm 2 show two portions with different contrasts, and diameters of 5.97 and 22.49 nm, respectively; 3D elemental distribution in these glasses from LEAP tomography shows areas of high Zn concentration near the CdSe QDs. Iso-concentration images obtained using visualization software show that Cd-rich clusters were not completely covered by the Zn-rich shells in the glass after 15 min irradiation that resulted emission due to the surface defects of CdSe QDs. As the irradiation time increased to 60 min, the Znrich cluster gradually surrounded the Cd-rich core to form shells that eliminated the surface defects. During laser irradiation, CdSe QDs precipitated first due to the high degree of supersaturation of Cd and Se followed by the sequential incorporation of Zn on the Cd-rich QDs forming shells.