Nonradiative recombination processes in nanocrystalline silicon

众所周知，纳米硅具有很高的光致发光量子效率。脉冲激光烧蚀法制备的硅纳米晶由于其尺寸和表面状态可以通过沉积参数来控制，因此是一种很有前途的材料。我们还利用射频溅射方法在SiO_2或SiH_2基质中制备了纳米级的Si。这些材料的光致发光特性。由聚乳酸制备的纳米硅的光致发光峰值能量在1.7 eV到2.0 eV之间变化。在前人的工作中，一些作者认为这种位移是由量子尺寸效应引起的。结果表明，该峰是1.7 eV峰和2.0 eV峰的叠加，其发光特性与射频溅射制备的SiO_2或SiH_2基质中纳米硅的发光特性相似。合金化降低了发光强度的温度猝灭，导致了室温下较大的发光强度。我们没有观察到发光强度与缺陷密度之间的关系。根据发光强度随温度的变化，讨论了合金中的非辐射复合过程。我们得出结论，合金化引起的带隙起伏减少了向非辐射缺陷中心的跃迁。尽管a-Si合金和Si纳米晶的发光中心可能不同，但从非辐射复合的观点来看，高的发光效率的来源应该是相似的。

It is well known that nanocrystalline Si shows large photoluminescence quantum efficiency. The silicon nanocrystallites prepared by pulsed laser ablation method are a promising material since the size and surface condition can be controlled by deposition parameters. We also prepared nanoscale Si in SiO2 matrix or SiH2 matrix by RF sputtering methods. The photoluminescence(PL)properties of these materials. The PL peak energy of nc-Si prepared by PLA varied from 1.7 eV to 2.0 eV.In previous works, some authors concluded that the shift is originated to be quantum size effect. We found that the this peak is a super position of 1.7 ev and 2.0 ev peaks.The PL feature of nc-Si prepared by PLA was similar to that of nanoscale Si in SiO2 matrix or SiH2 matrix prepared by RF sputtering. Temperature quenching of the PL intensity reduced by alloying and resulted in the large PL intensity at room temperature. We could not observe a correlation between PL intensity and defect density. Nonradiative recombination processes in the alloys were discussed in terms of temperature dependence of PL intensity. We concluded bandgap fluctuation induced by alloying reduced a transition to the nonradiative defect center in these systems. Although the PL center of the a-Si alloy and Si nanocrystallites may different, the origin of the large PL efficiency should be similar in a viewpoint of nonradiative recombination.