Ultrafast Photoluminescence in Quantum-Confined Silicon Nanocrystals Arises from an Amorphous Surface Layer
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- 作者：Daniel C. Hannah ; Jihua Yang ; Nicolaas J. Kramer ; George C. Schatz ; Uwe R. Kortshagen ; Richard D. Schaller
- 刊名：ACS Photonics
- 出版年：2014
- 出版时间：October 15, 2014
- 年：2014
- 卷：1
- 期：10
- 页码：960-967
- 全文大小：543K
- ISSN：2330-4022
文摘
Here, we examine ultrafast photoluminescence produced from plasma-grown, colloidal silicon nanocrystals as a function of both particle size and lattice crystallinity. In particular, we quantify the decay time and spectral profiles of nominally few-picosecond direct-gap emission previously attributed to phononless electron鈥揾ole recombination. We find that the high-energy (400鈥?00 nm, 2鈥? eV) photoluminescence component consists of two decay processes with distinct time scales. The fastest photoluminescence exhibits an 鈭?0 ps decay constant largely independent of emission energy and particle size. Importantly, nearly identical temporal components and blue spectral features appear for amorphous particles. We thus associate high-energy, rapid emission with an amorphous component in all measured samples, as supported by Raman analysis and molecular dynamics simulation. Based on these observations, we advise that the observed dynamics proceed too slowly to originate from intraband carrier thermalization and instead suggest a nonradiative origin associated with the amorphous component.