Core and valence exciton formation in x-ray absorption, x-ray emission and x-ray excited optical luminescence from passivated Si nanocrystals at the Si L2,3 edge
Core and valence exciton formation in x-ray absorption, x-ray emission and x-ray excited optical luminescence from passivated Si nanocrystals at the Si L2,3 edge
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Si L2,3 边缘钝化硅纳米晶体的 X 射线吸收、X 射线发射和 X 射线激发光学发光中的核心和价态激子形成
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
M. Hunt
中科院分区：
文献类型：
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作者：
L. Šiller;S. Krishnamurthy;L. Kjeldgaard;B. Horrocks;Y. Chao;A. Houlton;A. Chakraborty;M. Hunt
用共振非弹性X射线散射（RIXS）、X射线吸收光谱和X射线激发光致发光（XEOL）测量了窄尺寸分布（直径2.2 ± 0.4nm）钝化Si纳米晶的Si L2，3边上元素特定的填充和空电子态。这些技术已被用来直接测量吸收和发光特定的本地硅微晶核心。与体硅相比，纳米晶体的吸收光谱发生了深刻的变化，并观察到新的功能，在SiO2-RIXS。核心和价带激子形成，促进了纳米晶体内的电子和空穴的空间限制的明确签名，观察到，连同由于量子限制带变窄。12 K下的XEOL在橙子发光的阈值处显示出极其尖锐的特征（即，在λ 1.56eV（792 nm）处），我们将其归因于价态激子的复合，从而提供了λ能带隙的下限。
Resonant inelastic x-ray scattering (RIXS), x-ray absorption spectroscopy and x-ray excited optical luminescence (XEOL) have been used to measure element specific filled and empty electronic states over the Si L2,3 edge of passivated Si nanocrystals of narrow size distribution (diameter 2.2 ± 0.4 nm). These techniques have been employed to directly measure absorption and luminescence specific to the local Si nanocrystal core. Profound changes occur in the absorption spectrum of the nanocrystals compared with bulk Si, and new features are observed in the nanocrystal RIXS. Clear signatures of core and valence band exciton formation, promoted by the spatial confinement of electrons and holes within the nanocrystals, are observed, together with band narrowing due to quantum confinement. XEOL at 12 K shows an extremely sharp feature at the threshold of orange luminescence (i.e., at ∼1.56 eV (792 nm)) which we attribute to recombination of valence excitons, providing a lower limit to the nanocrystal band gap.