Nonradiative recombination processes in nanocrystalline silicon

众所周知，纳米晶硅具有较高的光致发光量子效率。脉冲激光烧蚀法制备的硅纳米晶是一种很有前途的材料，其尺寸和表面状况可以通过沉积参数来控制。我们还采用射频溅射的方法在SiO2基体或SiH2基体上制备了纳米级Si。这些材料的光致发光（PL）性能。PLA制备的nc-Si的PL峰值能量在1.7 ~ 2.0 eV之间变化。在以往的研究中，一些作者认为这种位移起源于量子尺寸效应。我们发现这个峰是1.7 ev和2.0 ev峰的叠加位置。PLA制备的nc-Si的发光特性与RF溅射制备的SiO2基体或SiH2基体中的纳米Si相似。合金的合金化降低了光强的温度淬火，导致室温下光强较大。我们没有观察到PL强度和缺陷密度之间的相关性。从PL强度的温度依赖性角度讨论了合金的非辐射复合过程。我们得出结论，合金引起的带隙波动减少了这些体系向非辐射缺陷中心的转变。虽然a-Si合金和Si纳米晶的发光中心可能不同，但从非辐射复合的角度来看，大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.