Time-resolved photoluminescence spectroscopy of the initial oxidation stage of small silicon nanocrystals

Dohnalová, Kateřina; Kůsová, Kateřina; Pelant, I.

doi:10.1063/1.3141481

Cited by 50 publications

(53 citation statements)

References 24 publications

(18 reference statements)

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“…25 On the other hand, luminescence enhancement has been observed after oxidation of Si-NCs produced by other methods, which has been attributed to an oxidation induced passivation of DBs. 11,14,15,30,[40][41][42][43][44] Distinct initial surface passivation and oxidation conditions may explain the apparent discrepancy between different studies. In an investigation where the oxidation approach of reducing the NCs size has been explored, the light emission of the smaller NCs obtained has been associated with defects, 1 in line with findings for Si nanocrystals embedded in amorphous SiO 2 , 45 and porous silicon.…”

Section: -35mentioning

confidence: 61%

“…29 In previous investigations of Si-NCs fabricated by other techniques, it has been found that oxidation may also result in a redshift of the NCs photoemission. 26,30,31 Theoretical calculations indicate that this could originate from the introduction of intragap energy levels by interfacial Si=O bonds, 26,27,32 and Si-O-Si surface bridges.…”

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confidence: 99%

“…In a previous study of photoluminescence (PL) from confined exciton recombination in Si-NCs present in freshly prepared porous silicon, a two stage behavior of the PL intensity as a function of oxidation time has been observed. 30 Namely, an initial PL increase, which has been interpreted as resulting from passivation of DB defects, followed by a PL quenching due to oxygen related surface states formed during oxidation. 30 Our experimental data seems to support this interpretation.…”

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confidence: 99%

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Oxidation of freestanding silicon nanocrystals probed with electron spin resonance of interfacial dangling bonds

et al. 2011

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The oxidation of freestanding silicon nanocrystals (Si-NCs) passivated with Si-H bonds has been investigated for a wide range of oxidation times (from a few minutes to several months) by means of electron spin resonance (ESR) of dangling bonds (DBs) naturally incorporated at the interface between the NCs core and the developing oxide shell. These measurements are complemented with surface chemistry analysis from Fourier-transform infrared spectroscopy. Two surface phenomena with initiation time thresholds of 15 minutes and 30 hours are inferred from the dependence of ESR spectra on oxidation time. The first initiates before oxidation of surface Si-Si bonds and destruction of the NCs hydrogen termination takes place (induction period), and results in a decrease of the DBs density and a localization of the DBs orbital at the central Si atom. Within the Cabrera-Mott oxidation mechanism, we associate this process with the formation of intermediate interfacial configurations, resulting from surface adsorption of water and oxygen molecules. The second surface phenomenon leads to a steep increase of the defects density and correlates with the formation of surface Si-O-Si bridges, lending experimental support to theoretically proposed mechanisms for interfacial defect formation involving the emission of Si interstitials at the interface between crystalline Si and the growing oxide.

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Section: -35mentioning

confidence: 61%

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confidence: 99%

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confidence: 99%

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Oxidation of freestanding silicon nanocrystals probed with electron spin resonance of interfacial dangling bonds

et al. 2011

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“…The PL emission observed in embedded films with both red and blue Si-NCs before thermal annealing is similar to that observed in the colloidal solutions (Figure 7a). Since the SOG around the Si-NCs is not chemically bonded to them, the embedded film emission is ascribed to the quantum confinement mechanism, as proposed by other authors for similar films [25,50]. The thermal annealing also appears to cause the loss of the H-passivated characteristics of the Si-NCs, modifying its configuration into an oxygen-passivated surface.…”

Section: Photoluminescence Propertiesmentioning

confidence: 60%

Luminescent Properties of Silicon Nanocrystals:Spin on Glass Hybrid Materials

et al. 2017

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Abstract:The photoluminescence characteristics of films consisting of Si nanocrystals either coated with or embedded into Spin on Glass (SOG) were studied. Si nanocrystals showing red or blue luminescence when suspended in alcohol solution were obtained from porous silicon films. These were then either deposited in Si substrates and coated with SOG, or mixed in an SOG solution that was later spun on Si substrates. Both types of films were thermally annealed at 1100 • C for three hours in N 2 atmosphere. Transmission electron microscopy measurements showed a mean diameter of 2.5 nm for the Si nanocrystals, as well as the presence of polycrystalline Si nanoagglomerates. These results were confirmed by X-ray diffraction studies, which revealed the (111), (220) and (311) Bragg peaks in Si nanocrystals. Fourier transform infrared spectroscopy studies showed that the coated films present higher chemical reactivity, promoting the formation of non-stoichiometric SiO 2 , while the embedded films behave as a stoichiometric SiO 2 after the thermal annealing. The PL (photoluminescence) characterization showed that both embedded and coated films present emission dominated by the Quantum Confinement Effect before undergoing any thermal treatment. After annealing, the spectra were found to be modified only in the case of the coated films, due to the formation of defects in the nanocrystals/SiO 2 interface.

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“…13,49,57,65,67,72,[125][126][127][128] The presence of Si surface radicals on Si NPs has been supported by electron paramagnetic resonance (EPR) spectroscopy, and various causes for their existence have been suggested. Two common causes that have been suggested are the formation of lowquality or disordered surface oxides, yielding EPR-active SiO 2 -Si, 56,72 and desorption of hydrogen from the H-Si NP surface, which yields EPR-active Si 3 -Si.…”

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confidence: 99%

Investigation into Effects of Instability and Reactivity of Hydride-Passivated Silicon Nanoparticles on Interband Photoluminescence

Radlinger¹

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While silicon has long been utilized for its electronic properties, its use as an optical material has largely been limited due to the poor efficiency of interband transitions. However, discovery of visible photoluminescence (PL) from nanocrystalline silicon in 1990 triggered many ensuing research efforts to optimize PL from nanocrystalline silicon for optical applications. Currently, use of photoluminescent silicon nanoparticles (Si NPs) is commercially limited by: 1) the instability of the energy and intensity of the PL, and 2) the low quantum yield of interband PL from Si NPs.Herein, red-emitting, hydrogen-passivated silicon nanoparticles (H-Si NPs) were synthesized by thermally-induced disproportionation of a HSiCl 3 -derived (HSiO 1.5 )n polymer. The H-Si NPs produced by this method were then subjected to various chemical and physical environments to assess the long-term stability of the optical properties as a function of changing surface composition. This dissertation is intended to elucidate correlations between the reported PL instability and the observed changes in the Si NP surface chemistry over time and as a function of environment.First, the stability of the H-Si NP surface at slightly elevated temperatures towards reactivity with a simple alkane was probed. The H-Si NPs were observed by FT-IR spectroscopy to undergo partial hydrosilylation upon heating in refluxing hexane, in addition to varying degrees of surface oxidation. The unexpected reactivity of the Si surface in n-hexane supports the unstable nature of the H-Si NP surface, and furthermore implicates the presence of highly-reactive Si radicals on the surfaces of the Si NPs. We propose that reaction of alkene impurities with the Si surface radicals is largely responsible for the observed surface alkylation. However, we also present an alternate ii mechanism by which Si surface radicals could react with alkanes to result in alkylation of the surface.Next, the energy and intensity stability of the interband PL from H-Si NPs in the presence of a radical trap was probed. Upon addition of (2,2,6,6,-tetramethyl-piperidin-1-yl)oxyl (TEMPO), the energy and intensity of the interband transition was observed to change over time, dependent on the reaction conditions. First, when the reaction occurred at 4ºC with minimal light exposure, the interband transition exhibited a gradual hypsochromic shift to between 595 nm and 655 nm, versus the λ max of the original low energy emission peak at 700 nm, depending on the amount of TEMPO in the sample.Second, when the reaction proceeded at room temperature with frequent exposure to 360 nm irradiation, the original interband transition at 660 nm was quenched while a new peak at 575 nm developed. Based on all the data collected and analyzed, we assign the 595 -655 nm transition as due to interband exciton recombination from Si NPs with reduced diameters relative to the original Si NPs. We furthermore assign the 575 nm transition as due to an oxide-related defect state resulting from rapid oxidation of pho...

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Time-resolved photoluminescence spectroscopy of the initial oxidation stage of small silicon nanocrystals

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Cited by 50 publications

References 24 publications

Oxidation of freestanding silicon nanocrystals probed with electron spin resonance of interfacial dangling bonds

Oxidation of freestanding silicon nanocrystals probed with electron spin resonance of interfacial dangling bonds

Luminescent Properties of Silicon Nanocrystals:Spin on Glass Hybrid Materials

Investigation into Effects of Instability and Reactivity of Hydride-Passivated Silicon Nanoparticles on Interband Photoluminescence

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