The big red shift of photoluminescence of Mn dopants in strained CdS: a case study of Mn-doped MnS-CdS heteronanostructures.

The red photoluminescence of Mn dopants in MnS−CdS heteronanostructures has been observed for the first time. The red photoluminescence at 650 nm derives from emission due to the 4T1 → 6A1 transition of Mn2+ dopants in a CdS matrix exposed to gigapascal-level lattice stress. HRTEM, FFT, XRD, and optical studies revealed that the lattice of Mn-doped CdS is compressed to match that of MnS when CdS crystallizes at the MnS surface to form MnS−CdS heteronanostructures. The photoluminescence decay times of such Mn dopants are on the order of nanoseconds because of the spin-flip interactions between Mn dopants and free carriers in the CdS matrix.