EPR spectra of Mn2+-doped ZnS quantum dots

Powder Mn2+ EPR spectra of 5-nm ZnS:Mn quantum dots have been analyzed in detail to account for all the observed fine spectral features. The same spectral features are observed in samples with low doping of Mn2+ (0.003-0.008%), showing 10 weak forbidden transitions between the six-line pattern of the M-S = -(1)/(2) to M-S = (1)/(2) transition for the six M-1 values. Spectral simulations have been performed with the Simfonia program with parameters g(xx) = 2.0064, g(yy) = 2.0064, g(zz) = 2.0066, D = 37.4 x 10(-4) cm(-1), E = 12.5 x 10(-4) cm(-4), A(xx) = 63.9 x 10(-4) cm(-1), A(yy) = 64.0 x 10(-4) cm(-1), and A(zz) = 64.4 x 10(-4) cm(-1), suggesting a lower than T-d site symmetry for the doped Mn2+ in the cubic ZnS structure. At higher doping concentration (15.9%), a single broad line is observed with isotropic g and A.