CUED Publications database

Light absorption in silicon quantum dots embedded in silica

Mirabella, S and Agosta, R and Franzó, G and Crupi, I and Miritello, M and Lo Savio, R and Di Stefano, MA and Di Marco, S and Simone, F and Terrasi, A (2009) Light absorption in silicon quantum dots embedded in silica. Journal of Applied Physics, 106. ISSN 0021-8979

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The photon absorption in Si quantum dots (QDs) embedded in SiO 2 has been systematically investigated by varying several parameters of the QD synthesis. Plasma-enhanced chemical vapor deposition (PECVD) or magnetron cosputtering (MS) have been used to deposit, upon quartz substrates, single layer, or multilayer structures of Si-rich- SiO 2 (SRO) with different Si content (43-46 at. %). SRO samples have been annealed for 1 h in the 450-1250 °C range and characterized by optical absorption measurements, photoluminescence analysis, Rutherford backscattering spectrometry and x-ray Photoelectron Spectroscopy. After annealing up to 900 °C SRO films grown by MS s how a higher absorption coefficient and a lower optical bandgap (∼2.0 eV) in comparison with that of PECVD samples, due to the lower density of Si-Si bonds and to the presence of nitrogen in PECVD materials. By increasing the Si content a reduction in the optical bandgap has been recorded, pointing out the role of Si-Si bonds density in the absorption process in small amorphous Si QDs. Both the photon absorption probability and energy threshold in amorphous Si QDs are higher than in bulk amorphous Si, evidencing a quantum confinement effect. For temperatures higher than 900 °C both the materials show an increase in the optical bandgap due to the amorphous-crystalline transition of the Si QDs. Fixed the SRO stoichiometry, no difference in the optical bandgap trend of multilayer or single layer structures is evidenced. These data can be profitably used to better implement Si QDs for future PV technologies. © 2009 American Institute of Physics.

Item Type: Article
Divisions: Div B > Photonics
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 18:57
Last Modified: 11 Jan 2018 02:44