Valenta J, Greben M, Dyakov S A, Gippius N A, Hiller D, Gutsch S, Zacharias M
Charles University, Faculty of Mathematics & Physics, Department of Chemical Physics & Optics, Prague, Czechia.
Skolkovo Institute of Science and Technology, Moscow, Russia.
Sci Rep. 2019 Aug 2;9(1):11214. doi: 10.1038/s41598-019-47825-x.
Thin layers of silicon nanocrystals (SiNC) in oxide matrix with optimized parameters are fabricated by the plasma-enhanced chemical vapor deposition. These materials with SiNC sizes of about 4.5 nm and the SiO barrier thickness of 3 nm reveal external quantum yield (QY) close to 50% which is near to the best chemically synthetized colloidal SiNC. Internal QY is determined using the Purcell effect, i.e. modifying radiative decay rate by the proximity of a high index medium in a special wedge-shape sample. For the first time we performed these experiments at variable temperatures. The complete optical characterization and knowledge of both internal and external QY allow to estimate the spectral distribution of the dark and bright NC populations within the SiNC ensemble. We show that SiNCs emitting at around 1.2-1.3 eV are mostly bright with internal QY reaching 80% at room temperature and being reduced by thermally activated non-radiative processes (below 100 K internal QY approaches 100%). The mechanisms of non-radiative decay are discussed based on their temperature dependence.
通过等离子体增强化学气相沉积法制备了具有优化参数的氧化物基质中的硅纳米晶体（SiNC）薄层。这些SiNC尺寸约为4.5nm且SiO势垒厚度为3nm的材料显示出接近50%的外量子产率（QY），这接近最佳化学合成的胶体SiNC。内量子产率是利用珀塞尔效应确定的，即在特殊楔形样品中通过高折射率介质的接近来改变辐射衰减率。我们首次在可变温度下进行了这些实验。完整的光学表征以及对内量子产率和外量子产率的了解使得能够估计SiNC集合体内暗态和亮态纳米晶体群体的光谱分布。我们表明，在1.2 - 1.3 eV左右发射的SiNC大多是亮态的，室温下内量子产率达到80%，并因热激活的非辐射过程而降低（低于100K时内量子产率接近100%）。基于非辐射衰减的温度依赖性讨论了其机制。
