Influence of the surface termination on the light emission of crystalline silicon nanoparticles


The light emission properties of silicon crystalline nanoparticles (SiNPs) have been investigated using steady-state and time-resolved photoluminescence measurements carried out at 12 K and at room temperature. To enable a comparative study of the role of surface terminal groups on the optical properties, we investigated SiNPs-H ensembles with the same mean NP diameter but differing on the surface termination, namely organic-functionalized with 1-dodecene (SiNPs-C12) and H-terminated (SiNPs-H). We show that although the spectral dependence of the light emission is rather unaffected by surface termination, characterized by a single broad band peaking at similar to 1.64 eV, both the exciton recombination lifetimes and quantum yields display a pronounced dependence on the surface termination. Exciton lifetimes and quantum yields are found to be significantly lower in SiNPs-H compared SiNPs-C12. This difference is due to distinct non-radiative recombination probabilities resulting from inter-NP exciton migration, which in SiNPs-C12 is inhibited by the energy barriers imposed by the bulky surface groups. The surface groups of organic-terminated SiPs are responsible for the inhibition of inter-NP exciton transfer, yielding a higher quantum yield compared to SiNPs-H. The surface oxidation of SiNPs-C12 leads to the appearance of a phenomenon of an exciton transference from to the Si core to oxide-related states that contribute to light emission. These excitons recombine radiatively, explaining why the emission quantum of the organic-terminated SiNPs is the same after surface oxidation of SiNPs-C12.




Science & Technology - Other Topics; Materials Science; Physics


Botas, AMP; Anthony, RJ; Wu, J; Rowe, DJ; Silva, NJO; Kortshagen, U; Pereira, RN; Ferreira, RAS

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This work is partially developed in the scope of the projects CICECO-Aveiro Institute of Materials (UID/CTM/50011/2013) and I3N (UID/CTM/50025/2013), financed by national funds through the Fundacao para a Ciencia e a Tecnologia/Ministerio da Educacao e Ciencia (FCT/MEC) and cofinanced by FEDER under the PT2020 Partnership Agreement. The authors acknowledge the financial support of the FCT (Fundacao para a Ciencia e a Tecnologia, Portugal) via project PTDC/FIS/112885/2009 and RECI/FIS-NAN/0183/2012 (FCOMP-01-0124-FEDER-027494) and the Danish Council for Strategic Research via the THINC Project (10-0939691DSF). AMPB thanks FCT for a PhD fellowship (SFRH/BD/104789/2014). RJA, DJR, and UK were primarily supported by the MRSEC program of the National Science Foundation (NSF) under award no. DMR-0819885 and DMR-1420013. The authors thank J Held and S Ehrenberg from University of Minnesota for their help in TEM measurements.

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