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首页> 外文期刊>Nanotechnology >Photoactivated processes in optical fibers: generation and conversion mechanisms of twofold coordinated Si and Ge atoms
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Photoactivated processes in optical fibers: generation and conversion mechanisms of twofold coordinated Si and Ge atoms

机译：光纤中的光活化过程：双重协调的Si和GE原子的产生和转换机制

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In this work we present an extensive investigation of nanoscale physical phenomena related to oxygen-deficient centers (ODCs) in silica and Ge-doped silica by means of first-principles calculations, including nudged-elastic band, electron paramagnetic resonance parameters calculations, and many-body perturbation theory (GW and Bethe-Salpeter equation) techniques. We show that by neutralizing positively charged oxygen monovacancies we can obtain model structures of twofold Si and Ge defects of which the calculated absorption spectra and singlet-to-triplet transitions are in excellent agreement with the experimental optical absorption and photo-luminescence data. In particular we provide an exhaustive analysis of the main exciton peaks related to the presence of twofold defects including long-range correlation effects. By calculating the reaction pathways and energy barriers necessary for the interconversion, we advance a double precursory origin of the E-alpha' and Ge(2) centers as due to the ionization of neutral oxygen monovacancies (Si-Si and Ge-Si dimers) and as due to the ionization of twofold Si and Ge defects. Furthermore two distinct structural conversion mechanisms are found to occur between the neutral oxygen monovacancy and the twofold Si (and Ge) atom configurations. Such conversion mechanisms allow to explain the radiation induced generation of the ODC(II) centers, their photobleaching, and also their generation during the drawing of optical fibers.
机译：在这项工作中，我们通过第一原理计算，在二氧化硅和GE掺杂二氧化硅中进行了广泛的纳米级物理现象，包括闪电带，电子顺磁共振参数计算，以及许多 - 对手扰动理论（GW和Bethe - Salpeter方程）技术。我们表明，通过中和带正电的氧单遗址，我们可以获得双重Si和Ge缺陷的模型结构，其中计算的吸收光谱和单次T态转变与实验光学吸收和光发光数据具有很好的一致性。特别地，我们提供了与具有长距离相关效果的双重缺陷的存在相关的主激子峰的详尽分析。通过计算相互转化所需的反应途径和能量屏障，我们推出了E-α和Ge（2）中心的双重前兆来源，因为由于中性氧单遗址的电离（Si-Si和Ge-Si二聚体）并且由于Twofold Si和Ge缺陷的电离。此外两个截然不同的结构转换机构找到的中性氧单空位和硅双重（和Ge）原子配置之间发生。这种转换机制允许解释辐射诱导的ODC（II）中心，它们的光漂白，以及它们在光纤的图中的产生。

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