Metastability of Mn${}^{3+}$ in ZnO driven by strong $d$(Mn) intrashell Coulomb repulsion: experiment and theory

Abstract

Depopulation of the Mn${}^{2+}$ state in ZnO:Mn upon illumination, monitored by quenching of the Mn${}^{2+}$ EPR signal intensity, was observed at temperatures below 80~K. Mn${}^{2+}$ photoquenching is shown to result from the Mn${}^{2+}$ $\to$ Mn${}^{3+}$ ionization transition, promoting one electron to the conduction band. Temperature dependence of this process indicates the existence of an energy barrier for electron recapture of the order of 1~meV. GGA$+U$ calculations show that after ionization of Mn${}^{2+}$ a moderate breathing lattice relaxation in the 3+ charge state occurs, which increases energies of $d$(Mn) levels. At its equilibrium atomic configuration, Mn${}^{3+}$ is metastable since the direct capture of photo-electron is not possible. The metastability is mainly driven by the strong intra-shell Coulomb repulsion between $d$(Mn) electrons. Both the estimated barrier for electron capture and the photoionization energy are in good agreement with the experimental values.

11 pages, 11 figures, 1 table

References in corpus (4)

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• A comparative study of ab initio nonradiative recombination rate calculations under different formalisms
• Optical Properties of Manganese Doped Wide Band Gap ZnS and ZnO
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