Evidence for photogenerated intermediate hole polarons in ZnO
Evidence for photogenerated intermediate hole polarons in ZnO
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DOI：
10.1038/ncomms7901
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发表时间：
2015-04
影响因子：
16.6
通讯作者：
H. Sezen;Honghui Shang;F. Bebensee;Chengwu Yang;Maria Buchholz;A. Nefedov;S. Heissler;Christian Carbogno;M. Scheffler;P. Rinke;C. Wöll
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文献类型：
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作者：
H. Sezen;Honghui Shang;F. Bebensee;Chengwu Yang;Maria Buchholz;A. Nefedov;S. Heissler;Christian Carbogno;M. Scheffler;P. Rinke;C. Wöll
尽管它们在氧化物光化学、光电子学和光化学中有着显著的重要性，但人们对极化子的寿命和结合能知之甚少。极化子代表了在初级光吸收过程中形成的激子解离后立即填充的关键中间步骤。在这里，我们提出了一种新的方法来研究一个重要的光活性氧化物，氧化锌，使用红外（IR）反射吸收光谱（IRRAS）的时间分辨率为100毫秒的光激发极化子。对于定义良好的（10 - 10）取向的ZnO单晶衬底，我们观察到强烈的红外吸收带在200毫电子伏左右，表现出明显的温度依赖性。基于第一性原理的电子结构计算的基础上，我们分配这些功能的中间耦合强度的空穴极化子。
Despite their pronounced importance for oxide-based photochemistry, optoelectronics and photovoltaics, only fairly little is known about the polaron lifetimes and binding energies. Polarons represent a crucial intermediate step populated immediately after dissociation of the excitons formed in the primary photoabsorption process. Here we present a novel approach to studying photoexcited polarons in an important photoactive oxide, ZnO, using infrared (IR) reflection–absorption spectroscopy (IRRAS) with a time resolution of 100 ms. For well-defined (10-10) oriented ZnO single-crystal substrates, we observe intense IR absorption bands at around 200 meV exhibiting a pronounced temperature dependence. On the basis of first-principles-based electronic structure calculations, we assign these features to hole polarons of intermediate coupling strength.