Dimensional dependence of the dynamics of the Mn 3d(5) luminescence in (Zn, Mn)S nanowires and nanobelts

Abstract

ZnS nanostructures of different morphologies, i.e., nanowires and nanobelts, have been ion implanted with Mn and subsequently annealed to obtain Zn1-xMnxS nanostructures. The Mn content x was adjusted to lie in the range from 4x10(-6)% to 4% corresponding to a variation of the mean Mn-Mn distance between about 200 and 2 nm, respectively. The Zn1-xMnxS nanowires have been studied by photoluminescence spectroscopy. The yellow Mn luminescence band indicates that the Mn2+ ions are incorporated on cation lattice sites replacing Zn. The temporal evolution of this internal Mn2+(3d(5)) luminescence is measured over 4 orders of magnitude in intensity. The decay behavior shows a clear dependence on the morphology of the nanostructure, in particular, on the ratio between the average Mn ion-killer center distance and the characteristic lateral size of the nanostructure. If the mean Mn-Mn distance is comparable to or smaller than the average Mn ion-killer center distance in the nanostructures, then concentration quenching of the Mn luminescence occurs similar to bulk. The nonexponential transients observed can be well described in the framework of a modified Forster model at reduced dimensionality. The photoluminescence (PL) behavior of the nanowires loses its one-dimensional character when the mean Mn ion-killer center distance becomes much smaller than the wire diameter. In contrast, the temporal PL behavior of the nanobelts is only purely two dimensional in this case and is of intermediate character between one dimensional and two dimensional otherwise.