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Light-Emission Performance of Silicon Nanocrystals Deduced from Single Quantum Dot Spectroscopy

机译：单量子点光谱法推导的硅纳米晶体的发光性能

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Spectra of individual silicon nanocrystals within porous Si grains are studied by the wide-field imaging microspectroscopy and their on-off blinking is detected by the confocal single-photon-counting microscopy. Observed spectral and blinking properties comprise all features reported before in differently prepared single Si nanocrystals (SiNCs). Former apparently contradictory results are shown to be due to different experimental conditions. When the effect of dark periods (off switching) is removed the common ultimate photoluminescence properties of SiO_2 passivated SiNCs are found, namely the quantum efficiency (QE) of about 10-20% up to the pumping rate corresponding to one exciton average excitation per quantum dot. At higher pump rates the QE is slowly decreasing as the 0.7th power of excitation. This is most likely due to Auger recombination which, however, seems to be weakened compared with measurements of nanocrystal assemblies. We conclude that SiNCs may be pumped above one exciton occupancy to yield a higher light emission, being advantageous for applications.
机译：通过宽视野成像显微技术研究了多孔硅晶粒内单个硅纳米晶体的光谱，并通过共聚焦单光子计数显微镜检测了它们的开关闪烁。观察到的光谱和闪烁特性包括以前在不同制备的单个Si纳米晶体（SiNC）中报告的所有特征。前明显矛盾的结果表明是由于不同的实验条件。当消除了暗周期（关断切换）的影响时，发现了SiO_2钝化的SiNC的共同的最终光致发光特性，即高达10％至20％的量子效率（QE），最高泵浦速率对应于每个量子的一个激子平均激发点。在较高的泵速下，QE随着激励的0.7次方而缓慢降低。这很可能是由于俄歇复合，然而，与纳米晶体组件的测量相比，俄歇复合似乎被削弱了。我们得出的结论是，可能会在一个激子占有率以上泵浦SiNC，以产生更高的发光量，这对应用程序是有利的。

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