Effect of hydrogen on the photoluminescence of Si nanocrystals embedded in a SiO2 matrix

Cheylan, S.; Elliman, R. G.

doi:10.1063/1.1338492

Cited by 105 publications

(67 citation statements)

References 13 publications

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“…This is evidence of H passivation of the remaining Si-dbs in the samples. As will be shown in section 3.3, increases of the PL intensity by comparable factors are observed, as is expected from the H passivation given that dbs act as efficient non-radiative recombination centers in both amorphous Si [27] and Si nanostructures [6,9,17,24,[29][30][31][32][33][34][35].…”

Section: Paramagnetic Defectsmentioning

confidence: 65%

From amorphous to crystalline silicon nanoclusters: structural effects on exciton properties

Borrero-González

Nunes

Guimarães

et al. 2011

J. Phys.: Condens. Matter

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Synchrotron x-ray absorption spectroscopy (XAS) and electron spin resonance (ESR) experiments were performed to determine, in combination with Raman spectroscopy and x-ray diffraction (XRD) data from previous reports, the structure and paramagnetic defect status of Si-nanoclusters (ncls) at various intermediate formation stages in Si-rich Si oxide films having different Si concentrations (y = 0.36-0.42 in Si y O 1−y ), fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition and isochronally (2 h) annealed at various temperatures (T a = 900-1100 • C) under either Ar or (Ar + 5%H 2 ) atmospheres. The corresponding emission properties were studied by stationary and time dependent photoluminescence (PL) spectroscopy in correlation with the structural and defect properties. To explain the experimental data, we propose crystallization by nucleation within already existing amorphous Si-ncls as the mechanism for the formation of the Si nanocrystals in the oxide matrix. The cluster-size dependent partial crystallization of Si-ncls at intermediate T a can be qualitatively understood in terms of a 'crystalline core-amorphous shell' Si-ncl model. The amorphous shell, which is invisible in most diffraction and electron microscopy experiments, is found to have an important impact on light emission. As the crystalline core grows at the expense of a thinning amorphous shell with increasing T a , the PL undergoes a transition from a regime dominated by disorder-induced effects to a situation where quantum confinement of excitons prevails.

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Section: Paramagnetic Defectsmentioning

confidence: 65%

From amorphous to crystalline silicon nanoclusters: structural effects on exciton properties

Borrero-González

Nunes

Guimarães

et al. 2011

J. Phys.: Condens. Matter

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“…It was already shown [18][19][20][21]32 that the passivation of nonradiative states and/or defects at the Si NC/matrix interface is an efficient method to increase the PL intensity in Si NCs without changing the original mechanism of PL emission. It was already reported 32 that the existence of one free bond, as for example the ·Siϵ Si 3 one, the so-called paramagnetic ͑P b ͒ defect center, is already sufficient to quench the PL of the corresponding Si NC.…”

Section: Discussionmentioning

confidence: 99%

“…It is well known that a thermal treatment at relatively low temperature ͑around 500°C͒ in a forming gas ͑FG͒ atmosphere passivates the Si dangling bonds at the nanocrystal surface, bringing as a consequence an increase of the PL intensity induced by the Si NCs. [18][19][20][21] Then, the appearance of two PL bands raises the following questions: ͑a͒ Is the passivation effect similar for both bands? ͑b͒ When the preannealing time is changed, how does it affect further FG treatment?…”

Section: Introductionmentioning

confidence: 99%

Optical and structural properties of Si nanocrystals produced by Si hot implantation

Sias

Behar

Boudinov

et al. 2007

Journal of Applied Physics

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It was already demonstrated that Si hot implantation followed by high-temperature annealing induces the formation of Si nanocrystals ͑Si NCs͒ which when excited in a linear excitation regime present two photoluminescence ͑PL͒ bands ͑at 780 and 1000 nm͒. We have undertaken the present work in order to investigate three features: First, to determine the origin of each band. With this aim we have changed the implantation fluence and the high-temperature annealing time. Second, to investigate the influence of the postannealing atmosphere on the PL recovering process after bombarding the Si NCs. Third, we have annealed the as-produced Si NCs in a forming gas ͑FG͒ atmosphere in order to observe the PL behavior of each band. The results have shown that the 780 nm PL band has its origin in radiative interfacial states, while the 1000 nm one is due to quantum size effects. From the experiments we have concluded that the PL recovery after the Si NCs irradiation strongly depends on the type of postannealing atmosphere. Finally, it was found that the FG treatment strongly affects the line shape of the PL spectrum.

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“…There are some reports on the increase of radiative efficiency by performing H passivation through standard forming gas annealing. [32][33][34] This way of passivating the Si-SiO 2 interface is well known and is routinely performed in CMOS technology. However, there is still no report on the quantification of the passivation effect and the correlation among defect concentration and PL yield.…”

Section: Introductionmentioning

confidence: 99%

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

Fernández

López

Garcı́a

et al. 2002

Journal of Applied Physics

260

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The correlation between the structural ͑average size and density͒ and optoelectronic properties ͓band gap and photoluminescence ͑PL͔͒ of Si nanocrystals embedded in SiO 2 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 SiO 2 . With this aim, we have recently developed a successful method for imaging Si nanocrystals in SiO 2 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 N 2 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 P b paramagnetic centers at the Si-SiO 2 nanocrystal-matrix interfaces, which have been measured by electron spin resonance. Consequently, the P b 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 0.26Ϯ0.03 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 SiO 2 is a fundamental transition spatially located at the Si-SiO 2 interface with the assistance of a local Si-O vibration.

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Effect of hydrogen on the photoluminescence of Si nanocrystals embedded in a SiO2 matrix

Cited by 105 publications

References 13 publications

From amorphous to crystalline silicon nanoclusters: structural effects on exciton properties

From amorphous to crystalline silicon nanoclusters: structural effects on exciton properties

Optical and structural properties of Si nanocrystals produced by Si hot implantation

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

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