Stimulated blue emission in reconstituted films of ultrasmall silicon nanoparticles

Nayfeh, Munir H.; Barry, Nicolas P. E.; Therrien, Joel; Akcakir, O.; Gratton, Enrico; Belomoin, G.

doi:10.1063/1.1347398

Cited by 155 publications

(93 citation statements)

References 15 publications

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“…It should be noted that the PL colour will be dominated by the main peak 604 nm here, which is red. In other cases, if the peak at 436 nm is much stronger than red peak, the PL colour would be dominated by blue [25,[39][40][41]. Figure 2b shows the PL after soft X-ray irradiation exposure X ¼ flux Â time ¼ 703 nA min, which was obtained after the XPS measurement.…”

Section: Photoluminescence Spectroscopymentioning

confidence: 99%

Soft X‐ray induced oxidation on acrylic acid grafted luminescent silicon quantum dots in ultrahigh vacuum

Chao

Wang

Pietzsch

et al. 2011

Physica Status Solidi (a)

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Water soluble acrylic acid grafted luminescent silicon quantum dots (Si-QDs) were prepared by a simplified method. The resulting Si-QDs dissolved in water and showed stable strong luminescence with peaks at 436 and 604 nm. X-ray photoelectron spectroscopy (XPS) was employed to examine the surface electronic states after the synthesis. The co-existence of the Si2p and C1s core levels infers that the acrylic acid has been successfully grafted on the surface of silicon quantum dots. To fit the Si2p spectrum, four components were needed at 99.45, 100.28, 102.21 and 103.24 eV. The first component at 99.45 eV (I) was assigned to Si-Si within the silicon core of the Si-QDs. The second component at 100.28 eV (II) was from Si-C. The third at 102.21 eV (III) was a sub-oxide state and the fourth at 103.24 eV (IV) was from SiO 2 at Si-QDs surface. With an increase in exposure to soft X-ray photons, the intensity ratio of the two peaks within the Si2p region A and B increased from 0.5 to 1.4 while the peak A intensity decreased, and eventually a steady state was reached. This observation is explained in terms of photon-induced oxidation taking place within the surface dangling bonds. As the PL profile for Si-QDs is influenced by the degree of oxidation within the nanocrystal structure, the inducement of oxidation by soft X-rays will play a role in the range of potential applications where such materials could be used -especially within biomedical labelling.

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Section: Photoluminescence Spectroscopymentioning

confidence: 99%

Soft X‐ray induced oxidation on acrylic acid grafted luminescent silicon quantum dots in ultrahigh vacuum

Chao

Wang

Pietzsch

et al. 2011

Physica Status Solidi (a)

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“…Recently, several groups, including ourselves, have prepared alkyl-passivated silicon nanocrystals. [5][6][7][8][9][10][11][12][13][14][15][16] These are SiNCs whose surface is capped by a monolayer of saturated hydrocarbon molecules and anchored to the Si core via covalent Si-C bonds. Although the particles contain a little oxide from their preparation, the alkyl monolayer protects the Si core and they are not oxidized further under ambient conditions.…”

mentioning

confidence: 99%

Optical luminescence from alkyl-passivated Si nanocrystals under vacuum ultraviolet excitation: Origin and temperature dependence of the blue and orange emissions

Chao

Houlton

Horrocks

et al. 2006

Applied Physics Letters

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The origin and stability of luminescence are critical issues for Si nanocrystals which are intended for use as biological probes. The optical luminescence of alkyl-monolayer-passivated silicon nanocrystals was studied under excitation with vacuum ultraviolet photons ͑5.1-23 eV͒. Blue and orange emission bands were observed simultaneously, but the blue band only appeared at low temperatures ͑Ͻ175 K͒ and with high excitation energies ͑Ͼ8.7 eV͒. At 8 K, the peak wavelengths of the emission bands were 430± 2 nm ͑blue͒ and 600± 2 nm ͑orange͒. The orange and blue emissions originate from unoxidized and oxidized Si atoms, respectively. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2216911͔Silicon nanostructures have attracted great interest since the observation of their efficient visible photoluminescence at room temperature in the early 1990s. 1-4 Silicon nanocrystals ͑SiNCs͒ are potential building blocks of future electronic and photonic devices. They also have promise as luminescent labels in biological applications, 5-9 because they show red-orange luminescence at small particle sizes ͑ca. 2 nm diam͒ and are not expected to show some aspects of the toxicity of cadmium-based semiconductors. However, the stability of SiNCs towards O 2 and H 2 O is a concern. Recently, several groups, including ourselves, have prepared alkyl-passivated silicon nanocrystals. [5][6][7][8][9][10][11][12][13][14][15][16] These are SiNCs whose surface is capped by a monolayer of saturated hydrocarbon molecules and anchored to the Si core via covalent Si-C bonds. Although the particles contain a little oxide from their preparation, the alkyl monolayer protects the Si core and they are not oxidized further under ambient conditions. 6 The reaction used to prepare the capping monolayer is sufficiently general to allow manipulation of the chemical functionality on the particle surface, e.g., for synthesis of DNA strands. 6 However, it is also important to characterize the physical properties, especially the luminescence, of these systems because the utility of the particles depends on their luminescence upon insertion into biological cells.Compared to the generally weak IR luminescence of bulk silicon ͑observed at low temperatures͒, the efficiency of photoluminescence ͑PL͒ from Si nanostructures is strongly increased due to the greater overlap of the electron and hole wave functions and the decrease in efficiency of nonradiative pathways. 17,18 A few electronic structure calculations on alkylated SiNCs have been made using density functional methods: these calculations include Si 29 clusters passivated with CH 3 or CH 2 ͑Ref. 19͒ and, more recently, alkyl monolayers up to C 4 H 9 on cluster sizes from Si 20 to Si 142 . 20 Theoretical work suggests that the band gap of SiNCs is little changed upon alkylation of the hydrogen-terminated particle surface, but the positions of the band edges are shifted significantly towards the vacuum level and the properties of the excited states are affected. 20 Experimental studies of the PL mechanism o...

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“…The particles are nearly spherical with 1 nm diameter, with insignificant size or shape dispersion 23 . The particles exhibit several novel properties including strong direct-like optical activity 18,19 , which enables detection of single particles 15 , gain and stimulated emission 16,17 , and nonlinear optical behavior, such as harmonic generation 20 . Electronically, electron affinity values drop to those characteristic of atoms and molecules, and single electron charging exceeds the thermal energy 21 .…”

Section: Methodsmentioning

confidence: 99%

“…The particles are produced by dispersion of (100) oriented, 1 -10 ohm-cm resistivity, ptype boron doped Si, by lateral anodization in hydrogen peroxide and HF acid [15][16][17][18][19][20][21][22]26 . Subsequent immersion in an ultra-sound acetone or water bath dislodges the ultrasmall particles.…”

Section: Methodsmentioning

confidence: 99%

Observation of linear solid-solid phase transformation in silicon nanoparticles

et al. 2012

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In bulk single crystal silicon, the semiconducting diamond to metallic ß-Sn phase transformation nucleates on defects, and is manifested by a sharp uptake in light absorption at a threshold of ~ 11 Gpa, accompanied with the creation of nanosized (20-50 nm) fragmentation domains. We report on the observation of linear uptakes in the absorption and in the luminescence, and with insignificant spectral change in ultrasmall 1 nm Si particles. We associate the gradual absorption uptake and luminescence yield with silicon-metal transformation on the surface. The insignificant change in the spectral content of the luminescence points to surface stability for particles, which are smaller than the bulk fragmentation domain. First-principle atomistic calculations yield absorption behavior that exhibits gradual uptake followed by sharp uptake at ~ 9-11 Gpa. The results point to the conclusion that two dimensional surface-like phase transformations are manifested by linear uptake in absorption and luminescence. a) m-nayfeh@illinois.edu 2

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Stimulated blue emission in reconstituted films of ultrasmall silicon nanoparticles

Cited by 155 publications

References 15 publications

Soft X‐ray induced oxidation on acrylic acid grafted luminescent silicon quantum dots in ultrahigh vacuum

Soft X‐ray induced oxidation on acrylic acid grafted luminescent silicon quantum dots in ultrahigh vacuum

Optical luminescence from alkyl-passivated Si nanocrystals under vacuum ultraviolet excitation: Origin and temperature dependence of the blue and orange emissions

Observation of linear solid-solid phase transformation in silicon nanoparticles

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