Spin configuration of T14 and A61 states in a manganese-doped wide band gap semiconductor

Abstract

We probe the spin configuration of manganese's $d$ states, namely $^{4}\mathrm{T}_{1}$ and $^{6}\mathrm{A}_{1}$, in doped semiconductor quantum dots (QDs) through spin-polarized scanning tunneling spectroscopy (SP-STS). We show that the two levels have opposing spin states. Experimentally, we probed the density of states (DOS) of the undoped and manganese-doped ZnS QDs, which have a wide band gap so that the $^{4}\mathrm{T}_{1}$ and $^{6}\mathrm{A}_{1}$ energies lie within the gap. The states were viewed with a nonmagnetic and a spin-polarized tip of a scanning tunneling microscope (STM). While a nonmagnetic tip could inject electrons into the $^{4}\mathrm{T}_{1}$ and withdraw electrons from the $^{6}\mathrm{A}_{1}$ state as well, the DOS derived with a spin-polarized tip evidenced that the tip could ``see'' only one of the two energy levels, whose spin state remained parallel to that of the tip. The intensity of DOS representing the $^{4}\mathrm{T}_{1}$ and $^{6}\mathrm{A}_{1}$ of manganese thereby depended on the mutual alignment of the magnetization vectors representing the tip and the $d$ states. We have inferred that the spin configuration of $^{4}\mathrm{T}_{1}$ and $^{6}\mathrm{A}_{1}$ states is mutually antiparallel in nature; such results have been the rationale of the photoluminescence (PL) emission in such manganese-doped QDs to possess an exceptionally long lifetime.