Optical Properties of Si Nanocrystals

Ковалев, Д. И.; Heckler, H.; Polisski, G.; Koch, F.

doi:10.1002/(sici)1521-3951(199910)215:2<871::aid-pssb871>3.0.co;2-9

Cited by 454 publications

(360 citation statements)

References 91 publications

(203 reference statements)

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“…In nanocrystals it is mainly attributed to exciton localization caused by quantum confinement. 17 Note that the full width at half-maximum (FWHM) of the NP peak (0.7 meV, deconvoluted) is smaller than the thermal broadening (k B T = 1.1 meV) at the temperature of 12 K. Similar observations have been made in other works 9,19 and can be regarded as strong evidence for single-nanocrystal emission, revealing its discrete nature of energy states. 20 Further support for this claim is provided by previous 21 and unpublished work that reports two-level blinking of many luminescing spots on similar samples, characteristic for single quantum emitters.…”

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confidence: 78%

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Transition from silicon nanowires to isolated quantum dots: Optical and structural evolution

et al. 2013

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The evolution of the structural and optical properties of a silicon core in oxidized nanowalls is investigated as a function of oxidation time. The same individual nanostructures are characterized after every oxidation step in a scanning electron microscope and by low-temperature photoluminescence, while a representative sample is also imaged in a transmission electron microscope. Analysis of a large number of recorded single-dot spectra and micrographs allows to identify delocalized and localized exciton emission from a nanowire as well as confined exciton emission of a nanocrystal. It is shown how structural transitions from one-to zero-dimensional confinement affect single-nanostructure optical fingerprints.

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Section: Fig 2 (Color Online) Pl Images and 50mentioning

confidence: 78%

“…TA and TO phonon replicas, as well as the zero-phonon transition, are frequently reported in the literature for silicon nanocrystals (see, e.g., Ref. 17 and references therein). The latter can even be observed in bulk material containing shallow donors, 18 due to exciton localization at the defect sites.…”

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confidence: 99%

Transition from silicon nanowires to isolated quantum dots: Optical and structural evolution

et al. 2013

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“…18 In order to extract information of the optical emission from stoichiometries closer to SiO 2 , special multilayered samples containing 20 periods of SiO 2 /SiO x bilayers nominally identical to the single layers were fabricated to increase their active volume and, in turn, their optical emission. In Fig.…”

Section: -2mentioning

confidence: 99%

Tailoring the surface density of silicon nanocrystals embedded in SiOx single layers

Hernández

Miska

Grün

et al. 2013

Journal of Applied Physics

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In this article, we explore the possibility of modifying the silicon nanocrystal areal density in SiO x single layers, while keeping constant their size. For this purpose, a set of SiO x monolayers with controlled thickness between two thick SiO 2 layers has been fabricated, for four different compositions (x ¼ 1, 1.25, 1.5, or 1.75). The structural properties of the SiO x single layers have been analyzed by transmission electron microscopy (TEM) in planar view geometry. Energy-filtered TEM images revealed an almost constant Si-cluster size and a slight increase in the cluster areal density as the silicon content increases in the layers, while high resolution TEM images show that the size of the Si crystalline precipitates largely decreases as the SiO x stoichiometry approaches that of SiO 2 . The crystalline fraction was evaluated by combining the results from both techniques, finding a crystallinity reduction from 75% to 40%, for x ¼ 1 and 1.75, respectively. Complementary photoluminescence measurements corroborate the precipitation of Si-nanocrystals with excellent emission properties for layers with the largest amount of excess silicon. The integrated emission from the nanoaggregates perfectly scales with their crystalline state, with no detectable emission for crystalline fractions below 40%. The combination of the structural and luminescence observations suggests that small Si precipitates are submitted to a higher compressive local stress applied by the SiO 2 matrix that could inhibit the phase separation and, in turn, promotes the creation of nonradiative paths. V C 2013 AIP Publishing LLC.

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“…Figures 11(a) and 11(b) show the values of σ abs for samples P2 and I3, respectively at the excitation wavelengths of 488 nm and 457 nm. In sample P2 [ figure 11(a)], σ abs decreases with the detection energy due to the reduction of the density of absorbing states in smaller nanocrystals, in good agreement with results reported by Kovalev et al [28]. In implanted samples the behaviour is quite different, since a slight increase of σ abs with the detection energy is observed.…”

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Si-nanocrystal-based LEDs fabricated by ion implantation and plasma-enhanced chemical vapour deposition

Perálvarez¹,

Barreto²,

Carreras³

et al. 2009

Nanotechnology

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Abstract. An in-depth study of the physical and electrical properties of Sinanocrystals embedded in silicon dioxide is presented. These layers were fabricated with different Si concentrations by both ion implantation and plasma-enhanced chemical vapour deposition. Subsequently, LEDs devices based on a metal-oxide-silicon configuration with a ∼350 nm polycrystalline Si top electrode and an active layer of about 45-50 nm, were fabricated in conventional lithography process. In order to optimize the device performances, prior to the top electrode deposition, the structural and photoluminescent properties of the active layers were exhaustively studied.Devices fabricated by ion implantation exhibit a combination of direct current and field-effect luminescence under a bipolar pulsed voltages excitation. The onset of the emission decreases with the Si excess from 6 to 3 V. The direct current emission is attributed to impact ionization, and is associated with the reasonably high current levels observed in current-voltage measurements. This behaviour is in good agreement with transmission electron microscopy images that revealed a continuous and uniform Si-nanocrystals distribution. The emission power efficiency is relatively low, ∼10 −3 %, and the emission intensity exhibits fast degradation rates, as revealed from accelerated aging experiments.Devices fabricated by chemical deposition only exhibit field-effect luminescence which onset decreases with the Si excess from 20 to 6 V. The absence of the continuous emission is explained by the observation of a 5-nm region free of nanocrystals, which strongly reduces the direct current through the gate. The main benefit of having this nanocrystal-free region is that tunnelling current flow assisted by nanocrystals is blocked by the SiO 2 stack so that power consumption is strongly reduced, which in return increases the device power efficiency up to 0.1 % . In addition, the accelerated aging studies reveal a 50% degradation rate reduction as compared to implanted structures.PACS numbers: 73.63. Bd, 78.67.Bf, 85.60.Jb Submitted to: Nanotechnology Si nanocrystal-based LEDs fabricated by ion implantation and PECVD 2

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Optical Properties of Si Nanocrystals

Cited by 454 publications

References 91 publications

Transition from silicon nanowires to isolated quantum dots: Optical and structural evolution

Transition from silicon nanowires to isolated quantum dots: Optical and structural evolution

Tailoring the surface density of silicon nanocrystals embedded in SiOx single layers

Si-nanocrystal-based LEDs fabricated by ion implantation and plasma-enhanced chemical vapour deposition

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