Abstract

We report on the results of analysis of optical absorption, EPR signals under optical excitation and magnetic susceptibility of hydrothermal Zn_{1 –x}Mn_xO single crystals. In the absorption spectra of polarized light at temperatures of 4.2 and 77.3 K, narrow intense a, b, c, and d lines are observed in the energy range 1.877–1.936 eV of light quanta. The spectrum of these lines differs significantly from the spectra of donor and acceptor excitons for ZnO:Co and ZnO:Ni. The intensity of allowed and forbidden EPR signals of the Mn²⁺(d⁵) ions does not change under the action of light in the impurity absorption band, while the EPR signals of uncontrollable Fe³⁺ (d⁵) ions under illumination practically disappear. New experimental results for Zn_{1 –x}Mn_xO lead to the conclusion that the d⁵/d⁴ donor level of the Mn²⁺ ion falls into the valence band, while the bandgap of Zn_{1 –x}Mn_xO contains several dangling bond hybrid (DBH) states due to hybridization of 3d orbitals of the Mn²⁺ ion with the p-bonds of the nearest O^2– oxygen ions. Electron transitions from the DBH states to the conduction band form a broad impurity absorption band of Zn_{1 –x}Mn_xO, below the edge of which the a, b, c, and d lines referred to as donor excitons [(h_loc + d⁵)e] and emerging as a result of Coulomb interaction of a free s-electron and a hole localized on DBH states (p + d⁵) are observed. The detection of donor excitons [(h_loc + d⁵)e] makes it possible to study in detail the DBH states in the bandgap, which is important for photocatalysis in the visible light range.

中文翻译：

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Zn 1 – x Mn x O带隙中的能态起源

摘要

我们报告了水热Zn _{1 – x} Mn _x O单晶在光激发和磁化率下的光吸收，EPR信号的分析结果。在温度为4.2和77.3 K的偏振光的吸收光谱中，在光量子的能量范围1.877–1.936 eV中观察到窄的强度a，b，c和d线。这些谱线的光谱与ZnO：Co和ZnO：Ni的供体和受体激子的光谱显着不同。Mn ²⁺（d ⁵的允许和禁止的EPR信号强度）离子在杂质吸收带中的光的作用下不会发生变化，而不可控的Fe ³⁺（d ⁵）离子在光照下的EPR信号实际上消失了。Zn _{1- x} Mn _x O的新实验结果得出以下结论：Mn ²⁺离子的d ⁵ / d ⁴供体能级落在价带中，而Zn _{1- x} Mn _x O的带隙包含多个悬空。Mn ²⁺离子的3 d轨道与p的杂化导致键杂化（DBH）状态-最近的O ^2–氧离子的键。电子从DBH态跃迁到导带形成了Zn _{1 – x} Mn _x O的宽杂质吸收带，在该吸收带的边缘以下，a，b，c和d线称为施主激子[[ h _loc + d ⁵）e ]并且观察到由于自由s电子与位于DBH态（p + d ⁵）上的空穴的库仑相互作用而出现的现象。供体激子的检测[（h _loc +d ⁵）e ]使得可以详细研究带隙中的DBH状态，这对于可见光范围内的光催化非常重要。