Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2

The correlation between the structural (average size and density) and optoelectronic properties [band gap and photoluminescence (PL)] of Si nanocrystals embedded in SiO2 is among the essential factors in understanding their emission mechanism. This correlation has been difficult to establish in the...

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Authors: Garrido Fernández, Blas, López de Miguel, Manuel, García, C., Pérez Rodríguez, Alejandro, Morante i Lleonart, Joan Ramon, Bonafos, Caroline, Carrada, Marzia, Claverie, Alain
Format: article
Status:Published version
Publication Date:2002
Country:España
Institution:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
Repository:Recercat. Dipósit de la Recerca de Catalunya
OAI Identifier:oai:recercat.cat:2445/24800
Online Access:https://hdl.handle.net/2445/24800
Access Level:Open access
Keyword:Ciència dels materials
Propietats òptiques
Materials science
Optical properties
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spelling Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2Garrido Fernández, BlasLópez de Miguel, ManuelGarcía, C.Pérez Rodríguez, AlejandroMorante i Lleonart, Joan RamonBonafos, CarolineCarrada, MarziaClaverie, AlainCiència dels materialsPropietats òptiquesMaterials scienceOptical propertiesThe correlation between the structural (average size and density) and optoelectronic properties [band gap and photoluminescence (PL)] of Si nanocrystals embedded in SiO2 is among the essential factors in understanding their emission mechanism. This correlation has been difficult to establish in the past due to the lack of reliable methods for measuring the size distribution of nanocrystals from electron microscopy, mainly because of the insufficient contrast between Si and SiO2. With this aim, we have recently developed a successful method for imaging Si nanocrystals in SiO2 matrices. This is done by using high-resolution electron microscopy in conjunction with conventional electron microscopy in dark field conditions. Then, by varying the time of annealing in a large time scale we have been able to track the nucleation, pure growth, and ripening stages of the nanocrystal population. The nucleation and pure growth stages are almost completed after a few minutes of annealing time at 1100°C in N2 and afterward the ensemble undergoes an asymptotic ripening process. In contrast, the PL intensity steadily increases and reaches saturation after 3-4 h of annealing at 1100°C. Forming gas postannealing considerably enhances the PL intensity but only for samples annealed previously in less time than that needed for PL saturation. The effects of forming gas are reversible and do not modify the spectral shape of the PL emission. The PL intensity shows at all times an inverse correlation with the amount of Pb paramagnetic centers at the Si-SiO2 nanocrystal-matrix interfaces, which have been measured by electron spin resonance. Consequently, the Pb centers or other centers associated with them are interfacial nonradiative channels for recombination and the emission yield largely depends on the interface passivation. We have correlated as well the average size of the nanocrystals with their optical band gap and PL emission energy. The band gap and emission energy shift to the blue as the nanocrystal size shrinks, in agreement with models based on quantum confinement. As a main result, we have found that the Stokes shift is independent of the average size of nanocrystals and has a constant value of 0.26±0.03 eV, which is almost twice the energy of the Si¿O vibration. This finding suggests that among the possible channels for radiative recombination, the dominant one for Si nanocrystals embedded in SiO2 is a fundamental transition spatially located at the Si¿SiO2 interface with the assistance of a local Si-O vibration.American Institute of Physics201220122002info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersion10 p.application/pdfhttps://hdl.handle.net/2445/24800Articles publicats en revistes (Enginyeria Electrònica i Biomèdica)reponame:Recercat. Dipósit de la Recerca de Catalunyainstname:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)InglésReproducció del document publicat a: http://dx.doi.org/10.1063/1.1423768Journal of Applied Physics, 2002, vol. 91, núm. 2, p. 798-807http://dx.doi.org/10.1063/1.1423768(c) American Institute of Physics, 2002info:eu-repo/semantics/openAccessoai:recercat.cat:2445/248002026-05-29T05:05:01Z
dc.title.none.fl_str_mv Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2
title Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2
spellingShingle Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2
Garrido Fernández, Blas
Ciència dels materials
Propietats òptiques
Materials science
Optical properties
title_short Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2
title_full Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2
title_fullStr Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2
title_full_unstemmed Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2
title_sort Influence of average size and interface passivation on the spectral emission of Si nanocrystals embedded in SiO2
dc.creator.none.fl_str_mv Garrido Fernández, Blas
López de Miguel, Manuel
García, C.
Pérez Rodríguez, Alejandro
Morante i Lleonart, Joan Ramon
Bonafos, Caroline
Carrada, Marzia
Claverie, Alain
author Garrido Fernández, Blas
author_facet Garrido Fernández, Blas
López de Miguel, Manuel
García, C.
Pérez Rodríguez, Alejandro
Morante i Lleonart, Joan Ramon
Bonafos, Caroline
Carrada, Marzia
Claverie, Alain
author_role author
author2 López de Miguel, Manuel
García, C.
Pérez Rodríguez, Alejandro
Morante i Lleonart, Joan Ramon
Bonafos, Caroline
Carrada, Marzia
Claverie, Alain
author2_role author
author
author
author
author
author
author
dc.subject.none.fl_str_mv Ciència dels materials
Propietats òptiques
Materials science
Optical properties
topic Ciència dels materials
Propietats òptiques
Materials science
Optical properties
description The correlation between the structural (average size and density) and optoelectronic properties [band gap and photoluminescence (PL)] of Si nanocrystals embedded in SiO2 is among the essential factors in understanding their emission mechanism. This correlation has been difficult to establish in the past due to the lack of reliable methods for measuring the size distribution of nanocrystals from electron microscopy, mainly because of the insufficient contrast between Si and SiO2. With this aim, we have recently developed a successful method for imaging Si nanocrystals in SiO2 matrices. This is done by using high-resolution electron microscopy in conjunction with conventional electron microscopy in dark field conditions. Then, by varying the time of annealing in a large time scale we have been able to track the nucleation, pure growth, and ripening stages of the nanocrystal population. The nucleation and pure growth stages are almost completed after a few minutes of annealing time at 1100°C in N2 and afterward the ensemble undergoes an asymptotic ripening process. In contrast, the PL intensity steadily increases and reaches saturation after 3-4 h of annealing at 1100°C. Forming gas postannealing considerably enhances the PL intensity but only for samples annealed previously in less time than that needed for PL saturation. The effects of forming gas are reversible and do not modify the spectral shape of the PL emission. The PL intensity shows at all times an inverse correlation with the amount of Pb paramagnetic centers at the Si-SiO2 nanocrystal-matrix interfaces, which have been measured by electron spin resonance. Consequently, the Pb centers or other centers associated with them are interfacial nonradiative channels for recombination and the emission yield largely depends on the interface passivation. We have correlated as well the average size of the nanocrystals with their optical band gap and PL emission energy. The band gap and emission energy shift to the blue as the nanocrystal size shrinks, in agreement with models based on quantum confinement. As a main result, we have found that the Stokes shift is independent of the average size of nanocrystals and has a constant value of 0.26±0.03 eV, which is almost twice the energy of the Si¿O vibration. This finding suggests that among the possible channels for radiative recombination, the dominant one for Si nanocrystals embedded in SiO2 is a fundamental transition spatially located at the Si¿SiO2 interface with the assistance of a local Si-O vibration.
publishDate 2002
dc.date.none.fl_str_mv 2002
2012
2012
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv https://hdl.handle.net/2445/24800
url https://hdl.handle.net/2445/24800
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Reproducció del document publicat a: http://dx.doi.org/10.1063/1.1423768
Journal of Applied Physics, 2002, vol. 91, núm. 2, p. 798-807
http://dx.doi.org/10.1063/1.1423768
dc.rights.none.fl_str_mv (c) American Institute of Physics, 2002
info:eu-repo/semantics/openAccess
rights_invalid_str_mv (c) American Institute of Physics, 2002
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv 10 p.
application/pdf
dc.publisher.none.fl_str_mv American Institute of Physics
publisher.none.fl_str_mv American Institute of Physics
dc.source.none.fl_str_mv Articles publicats en revistes (Enginyeria Electrònica i Biomèdica)
reponame:Recercat. Dipósit de la Recerca de Catalunya
instname:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
instname_str Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
reponame_str Recercat. Dipósit de la Recerca de Catalunya
collection Recercat. Dipósit de la Recerca de Catalunya
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15,812429

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