A Tale of Seemingly “Identical” Silicon Quantum Dot Families: Structural Insight into Silicon Quantum Dot Photoluminescence

Abstract

Two quantum dots, both alike in composition, but differing in structure, where we lay our scene. From broader classes, to bring deeper understanding, to the crystalline core that drives the quantum dot's sheen. In this contribution we examine two families of silicon quantum dots (SiQDs) that bring to mind the Capulets and the Montagues in Shakespeare's Romeo and Juliet because of their stark similarities and differences. SiQDs are

Band-Gap Tunability in Partially Amorphous Silicon Nanoparticles Using Single-Dot Correlative Microscopy

“…This is in agreement with our observations and two other studies by Thiessen et al , In fact, most studies in the literature do not exceed annealing over 1300 °C and do not pay special attention to the requirements of very slow cooling rates . This could mean that many materials earlier presented as crystalline Si-NPs might have been partially or fully amorphous, where the relatively thin amorphous Si shell would have been difficult to identify via XRD, Raman spectroscopy, or other means. Second, another study on a similar material by Thiessen et al arrived at an opposite interpretation that the PL is dominated by the crystalline Si core. However, their analysis is only indirect, and data were fitted assuming convergence to a bulk Si band gap.…”

“…Hence, our results strongly suggest that the analyzed Si-NPs are either fully amorphous or that the PL is dominated by the amorphous part of the Si-NP. This is a very interesting result, especially considering a recent study on a similar material system that suggests that it is the crystalline part that dominates the PL.…”

“…It is argued that such results indicate that it is the crystalline core, and not the amorphous shell, that dominates the optical properties. However, we would like to note that ref only offers an indirect correlation between the optical band gap and size and that the authors choose to fit the size dependence of both samples with a fixed bulk band-gap value, the crystalline Si one, instead of fitting the band gap to their data. Hence, we see controversy only in the interpretation and data analysis and not in the data itself, which should be further scrutinized.…”

Thermal Disproportionation for the Synthesis of Silicon Nanocrystals and Their Photoluminescent Properties

“…As for the heating process of silicon-rich oxide in the form of film, a theory of two thermal disproportionation stages was proposed, namely the precipitation of Si when the temperature was above 500°C and the crystallization of excess Si with the even higher temperature starting from ∼1,000°C (Gan et al, 2011). Since the PL had a close relationship with the size of SiNCs rather than that of amorphous silicon, the crystallization temperature therefore mattered (Thiessen et al, 2020). Amorphous materials cannot crystalize until the temperature reaches the threshold value.…”

Synthesis of Ag2S Based Quantum Dots with Near-infrared-II Fluorescence Emission in Water

“…其中, 以王强 斌团队 [11] 发现和研究的新型 Ag 2 S 基近红外 II 区荧光量 子点体系最具代表性. 尽管 Ag 2 S 基量子点的光致发光 效率很难与 Cd、Pb、Hg 基半导体量子点竞争, 但其稳 定的理化性质和优异的生物相容性使其成为近 10 年来 研究最多的近红外活体荧光探针 [11][12][13][14][15][16][17][18][19][20][21] . 量子点荧光探针的发展在一定程度上受到化学合 成工艺的影响.…”