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Thickness-dependent optimization of Er3+ light emission from silicon-rich silicon oxide thin films.

Cueff S, Labbé C, Jambois O, Garrido B, Portier X, Rizk R - Nanoscale Res Lett (2011)

Bottom Line: The Er3+ photoluminescence at 1.5 μm, normalized to the film thickness, was found five times larger for films 1 μm-thick than that from 50-nm-thick films intended for electrically driven devices.More Si excess has significantly increased the emission from "thin" films, up to ten times.This paves the way to the realization of highly efficient electrically excited devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP), ENSICAEN, CNRS, CEA/IRAMIS, Université de Caen, 14050 CAEN cedex, France. richard.rizk@ensicaen.fr.

ABSTRACT
This study investigates the influence of the film thickness on the silicon-excess-mediated sensitization of Erbium ions in Si-rich silica. The Er3+ photoluminescence at 1.5 μm, normalized to the film thickness, was found five times larger for films 1 μm-thick than that from 50-nm-thick films intended for electrically driven devices. The origin of this difference is shared by changes in the local density of optical states and depth-dependent interferences, and by limited formation of Si-based sensitizers in "thin" films, probably because of the prevailing high stress. More Si excess has significantly increased the emission from "thin" films, up to ten times. This paves the way to the realization of highly efficient electrically excited devices.

No MeSH data available.


Related in: MedlinePlus

Evolution of the estimated atomic percentage of agglomerated Si as a function of the film thickness. For as-deposited SRSO:Er layers deposited both at room temperature and at 500°C. The lines are guides to the eye. Inset: evolution of the refractive index and estimated increase of the compressive stress (right scale) for SiO2:Er and SRSO:Er as a function of the thickness.
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Figure 2: Evolution of the estimated atomic percentage of agglomerated Si as a function of the film thickness. For as-deposited SRSO:Er layers deposited both at room temperature and at 500°C. The lines are guides to the eye. Inset: evolution of the refractive index and estimated increase of the compressive stress (right scale) for SiO2:Er and SRSO:Er as a function of the thickness.

Mentions: with y the stoichiometry parameter (SiOy) detected by FTIR, implying x <y < 2. The atomic percentage of agglomerated Si, %Siagglo, can be estimated from ((y - x)/y)/(1 + x) and its evolution with thickness is shown in Figure 2 for the two series deposited at RT and 500°C. A single isolated Si atom is highly likely not able to act as a sensitizer, therefore this parameter (%Siagglo) includes the total population of Si-based sensitizers consisting in either Si-ncs, the so-called luminescent centers of Savchyn et al. [14], or the atomic scaled agglomerates suggested recently by our group [15]. To effectively play their sensitizing role, these entities should be located at less than about 1 nm of an optically active Er ion. Figure 2 shows that the agglomeration of Si is favored by increased Td and/or film thickness. While the raise of Td from RT to 500°C is expected to enhance the clustering of silicon during deposition, the most striking aspect is the pronounced increase of %Siagglo versus thickness. Note that the fraction of agglomerated Si in both RT-deposited and 500°C-deposited samples shows a similar increasing trend, but less pronounced for the former one, suggesting that this phenomenon stems from the influence of the thickness. Such an influence has been demonstrated earlier and assigned to the existence of a nucleation barrier for the formation of Si-nc as a function of the separation distance from the substrate, i.e. the film thickness [6-8]. This barrier is likely induced by the stress that is inversely proportional to film thickness [16], and thus prevents a complete phase separation of the SiOx system [17]. For an unchanged stoichiometry, the relative evolution of the internal stress of SiO2 deposited on Si substrate has been linked to its refractive index by the following relation [18]:(2)


Thickness-dependent optimization of Er3+ light emission from silicon-rich silicon oxide thin films.

Cueff S, Labbé C, Jambois O, Garrido B, Portier X, Rizk R - Nanoscale Res Lett (2011)

Evolution of the estimated atomic percentage of agglomerated Si as a function of the film thickness. For as-deposited SRSO:Er layers deposited both at room temperature and at 500°C. The lines are guides to the eye. Inset: evolution of the refractive index and estimated increase of the compressive stress (right scale) for SiO2:Er and SRSO:Er as a function of the thickness.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211489&req=5

Figure 2: Evolution of the estimated atomic percentage of agglomerated Si as a function of the film thickness. For as-deposited SRSO:Er layers deposited both at room temperature and at 500°C. The lines are guides to the eye. Inset: evolution of the refractive index and estimated increase of the compressive stress (right scale) for SiO2:Er and SRSO:Er as a function of the thickness.
Mentions: with y the stoichiometry parameter (SiOy) detected by FTIR, implying x <y < 2. The atomic percentage of agglomerated Si, %Siagglo, can be estimated from ((y - x)/y)/(1 + x) and its evolution with thickness is shown in Figure 2 for the two series deposited at RT and 500°C. A single isolated Si atom is highly likely not able to act as a sensitizer, therefore this parameter (%Siagglo) includes the total population of Si-based sensitizers consisting in either Si-ncs, the so-called luminescent centers of Savchyn et al. [14], or the atomic scaled agglomerates suggested recently by our group [15]. To effectively play their sensitizing role, these entities should be located at less than about 1 nm of an optically active Er ion. Figure 2 shows that the agglomeration of Si is favored by increased Td and/or film thickness. While the raise of Td from RT to 500°C is expected to enhance the clustering of silicon during deposition, the most striking aspect is the pronounced increase of %Siagglo versus thickness. Note that the fraction of agglomerated Si in both RT-deposited and 500°C-deposited samples shows a similar increasing trend, but less pronounced for the former one, suggesting that this phenomenon stems from the influence of the thickness. Such an influence has been demonstrated earlier and assigned to the existence of a nucleation barrier for the formation of Si-nc as a function of the separation distance from the substrate, i.e. the film thickness [6-8]. This barrier is likely induced by the stress that is inversely proportional to film thickness [16], and thus prevents a complete phase separation of the SiOx system [17]. For an unchanged stoichiometry, the relative evolution of the internal stress of SiO2 deposited on Si substrate has been linked to its refractive index by the following relation [18]:(2)

Bottom Line: The Er3+ photoluminescence at 1.5 μm, normalized to the film thickness, was found five times larger for films 1 μm-thick than that from 50-nm-thick films intended for electrically driven devices.More Si excess has significantly increased the emission from "thin" films, up to ten times.This paves the way to the realization of highly efficient electrically excited devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP), ENSICAEN, CNRS, CEA/IRAMIS, Université de Caen, 14050 CAEN cedex, France. richard.rizk@ensicaen.fr.

ABSTRACT
This study investigates the influence of the film thickness on the silicon-excess-mediated sensitization of Erbium ions in Si-rich silica. The Er3+ photoluminescence at 1.5 μm, normalized to the film thickness, was found five times larger for films 1 μm-thick than that from 50-nm-thick films intended for electrically driven devices. The origin of this difference is shared by changes in the local density of optical states and depth-dependent interferences, and by limited formation of Si-based sensitizers in "thin" films, probably because of the prevailing high stress. More Si excess has significantly increased the emission from "thin" films, up to ten times. This paves the way to the realization of highly efficient electrically excited devices.

No MeSH data available.


Related in: MedlinePlus