| Abstract
| - The two-dimensional (2D) dilute magnetic semiconductors Cd1-xMnxSe·L0.5 (L = ethylenediamine, oren, and 1,6-hexanediamine, or hda, x = 0−0.8) were synthesized in an autoclave at 120 °C. Ab initiostructure solution from X-ray powder diffraction reveals the host compound CdSe·hda0.5 (space group,Pbca, a = 6.8852 Å, b = 6.7894 Å, c = 27.4113 Å) is structurally analogous to CdSe·en0.5, except fora subtle difference in alignment of aliphatic diamine ligandsthe hda molecule deflects from the c axisand inclines toward the b axis. CdSe·L0.5 shows well-defined UV absorption and emission peaks, whichis attributed to a 2D exciton band edge transition due to size confinement effect in the c direction and theonly photoemission level is the 2D exciton ground state with a long lifetime (7 μs) and intrinsic linewidth (177 meV) at room temperature. When Cd2+ is partly substituted by Mn2+, a strong Mn2+-relatedluminescence peak at 2.12 eV (584 nm) is obtained at room temperature, which can be assigned to Mn2+internal transition (4T1 → 6A1); its excitation peak overlaps with the photoemission peak of the 2D excitonground state which indicates that the Mn2+ emission is driven by the 2D exciton ground-state transition.For x = 0.02, the photoluminescence intensity of Cd1-xMnxSe·hda0.5 reaches maximum and enhances 28times compared with that of Cd1-xMnxSe·en. When x< 0.05, the Mn2+ luminescence is a characteristicsingle-exponential decay process with a well-defined constant lifetime of 375 μs. Electron spin resonancespectra show that Mn2+ substitutes Cd2+ ion and forms a [MnSe3N] coordination tetrahedron and thatthere are isolated Mn2+ luminescence centers in Cd1-xMnxSe·hda0.5 (x < 0.05), which is the key factorfor their stronger luminescence character compared to Cd1-xMnxSe·en0.5.
- Cd1-xMnxSe·L0.5 (L = diamines) were synthesized and structurally analyzed. CdSe·L0.5 shows 2D band-edge exciton absorption/emission peaks, which are attributed to size confinement in the c direction. The Cd1-xMnxSe·L0.5 species exhibit a strong Mn2+ luminescence (2.12 eV) at room temperature, which is driven by the 2D exciton ground-state transition and have a luminescence enhancement with longer diamine molecules. The Mn2+ luminescence (x< 0.05) is a single-exponential decay process, and ESR spectra show that Mn2+ ions locate in [MnSe3N] tetrahedra and that their interaction is a key factor for the luminescence intensities.
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