Effect of atmospheric oxidation on the electronic and photoluminescence properties of silicon nanocrystal

Germanenko, I. N.; Dongol, M.; Pithawalla, Yezdi B.; El‐Shall, M. Samy; Carlisle, J. A.

doi:10.1351/pac200072010245

Cited by 20 publications

(27 citation statements)

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“…Other workers have observed both blue and orange bands in time-resolved PL from porous silicon 28 and during atmospheric oxidation of uncapped SiNCs ͑steady-state PL͒. [29][30][31] These studies are consistent with an interpretation that the blue emission is associated with Si oxides and that the orange PL is particle size dependent and derives from the quantum confinement effect in Si. Blue emission has been observed from Si and C implanted in SiO 2 matrices 32 and from carbon-plasma-implanted porous silicon, 33 but the orange emission of porous silicon disappeared after implantation.…”

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confidence: 82%

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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confidence: 82%

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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“…Individual spectra are offset on the y-axis for clarity. [49][50][51]. These studies are consistent with an interpretation that the blue emission is associated with Si oxides and that the orange PL is particle sizedependent and derives from the quantum-confinement effect in Si.…”

Section: Origin Of the Orange And Blue Pl Emissionsupporting

confidence: 87%

Optical Properties of Nanostructured Silicon

Chao

2011

Comprehensive Nanoscience and Technology

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“…1,6,16 Oxidation is one of the most important surface phenomena both from the fundamental and technological point of view. Oxidation of H terminated Si-NCs can readily take place in air at room temperature, 5,[18][19][20][21][22] whereas under pure molecular oxygen atmosphere higher temperatures are required. 23,24 Although efficient light emission from silane plasma Si-NCs in the range from near infrared to orange has been demonstrated, 1 the realization of green and blue light emission is necessary to materialize the full potential of Si-NCs.…”

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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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Effect of atmospheric oxidation on the electronic and photoluminescence properties of silicon nanocrystal

Cited by 20 publications

References 1 publication

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

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

Optical Properties of Nanostructured Silicon

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

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