Thermally induced Mn2+ partitioning between borosilicate glass and Sb2-xMnxSe3 nanocrystals reveals the origin of dual emission

Sb 2-x Mn x Se 3 diluted magnetic semiconductor nanocrystals (NCs) were grown in situ within an SNAB borosilicate glass matrix by the fusion–nucleation method. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy confirmed the formation of Mn-containing NCs with the orthorhombic Sb 2 Se 3 structure, average diameters of approximately 6.3 nm, and no detectable secondary crystalline phases. Increasing Mn concentration induces lattice expansion and Raman-mode blueshifts, consistent with substitutional incorporation of Mn 2+ into distorted pseudo-octahedral sites. Optical absorption reveals continuous bandgap narrowing from 3.02 to 2.26 eV, associated with Mn-induced electronic band restructuring involving a dominant CBM downshift of ≈ 0.65 eV and a smaller VBM upshift of ≈ 0.11 eV. Photoluminescence (PL) reveals two coexisting emission channels. The green band near 540 nm is assigned to the 4 T 1 ( 4 G)→ 6 A 1 ( 6 S) transition of Mn 2+ ions in tetrahedral sites of the glass matrix, whereas the red-to-near-infrared PL def. band, shifting from 1.79 to 1.68 eV, is associated with defect-related recombination in the Sb 2-x Mn x Se 3 NCs. Electron paramagnetic resonance (EPR) distinguishes Mn 2+ in pseudo-octahedral NC sites and tetrahedral glass sites, with hyperfine constants of ≈ 8.16 and ≈ 7.78 mT, respectively. The PL and EPR results demonstrate that thermal treatment promotes incorporation of Mn 2+ into the growing Sb 2 Se 3 NCs, while a residual Mn 2+ population is retained in tetrahedral sites in the glass matrix. This Mn 2+ partitioning between pseudo-octahedral sites in the Sb 2-x Mn x Se 3 NCs and tetrahedral sites in the borosilicate glass matrix reveals the origin of the dual-emission in the Sb 2-x Mn x Se 3 NCs/SNAB composite.