Photochemical processes in doped argon-neon core-shell clusters: The effect of cage size on the dissociation of molecular oxygen

Laarmann, Tim; Wabnitz, H.; Haeften, K. von; Möller, Thomas

doi:10.1063/1.2815798

Cited by 12 publications

(15 citation statements)

References 86 publications

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“…Another advantage of molecular beams is that clusters can be a e-mail: kvh6@le.ac.uk b Now at National Inst. for Material Physics, Bukarest, Romania co-doped in the vacuum by a pick-up process [18] or by codeposition with another gas onto a cold substrate [19,20]. In this paper we report on the molecular beam production of silicon clusters by DC magnetron sputtering and co-deposition with water onto a liquid nitrogen cooled substrate.…”

Section: Introductionmentioning

confidence: 99%

A novel approach towards the production of luminescent silicon nanoparticles: sputtering, gas aggregation and co-deposition with H2O

et al. 2009

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Abstract. Silicon clusters were produced by sputtering of a p-doped Si target and aggregation of the Si atoms in an argon gas atmosphere. The clusters were deposited in ultra high vacuum onto either (i) carbon transmission electron microscope (TEM) grids or (ii) a liquid nitrogen cooled finger on which a thick layer of ice was co-deposited during the exposure to the cluster beam. The ice layer containing the clusters was melted to form a liquid sample which showed luminescence peaking at 421 nm when excited at 307.5 nm. The luminescence is attributed to electron-hole recombination in oxygen deficient defects in the Si-SiO2 interface region. TEM images of the nanoparticles deposited on the carbon grids show spherical particles with diameters ranging from 4 to 50 nm, flake-like structures or nanotube-like shapes. Grids with higher deposited densities reveal clusters that are agglomerated into chains, TEM images of the dried liquid sample show a network of fibres indicating that growth into fibres is further promoted when the clusters gain mobility in the melted ice. PACS

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Section: Introductionmentioning

confidence: 99%

A novel approach towards the production of luminescent silicon nanoparticles: sputtering, gas aggregation and co-deposition with H2O

et al. 2009

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“…The passivation agents are interchangeable and doping via further codeposition is possible. 34 Thus, our method provides great flexibility, control and, potentially, an alternative to ion implantation.…”

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confidence: 99%

In situ passivation and blue luminescence of silicon clusters using a cluster beam/H2O codeposition production method

Brewer¹,

Haeften²

2009

Applied Physics Letters

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Si clusters are produced in a gas aggregation source and fly through ultrahigh vacuum onto a cold target where they are codeposited with water vapor. Melting of the ice yields immediately a suspension of nanoparticles that emits intense, nondegrading luminescence in the blue wavelength range. Spectroscopic analysis reveals a Si/SiO core-shell structure where the luminescence stems from oxygen deficient defects. The main advantage of our production method is that it yields the luminescent Si nanoparticles in one step. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3167355͔The process of light emission from materials with an indirect band gap in the bulk has attracted much interest both from a fundamental point of view and from the prospect of applications.1,2 Since the discovery of luminescence from porous silicon at room temperature 3,4 twenty years ago, fabrication of devices such as silicon-based light emitting diodes ͑Ref. 5͒ and lasers 6 has been achieved, and a large variety of types of photoluminescent silicon have been reported in the literature. These include nanowires and nanorods, 7-13 Si/SiO, Si/SiOH sandwich, and core-shell systems, [14][15][16] as well as Si clusters produced by laser photolysis 17,18 or by Si ion implantation in silica glass. 19,20 Furthermore, luminescent Si quantum dots in solutions have been investigated. [21][22][23] Nanoparticles in solution receive great attention because of applications in biological imaging and diagnostic labeling. 24In all the above-mentioned examples the production method plays a crucial role in the way the luminescence wavelength and luminescence efficiency is controlled. Some industrial production methods require specific conditions. For instance, in complementary metal-oxide-semiconductor ͑CMOS͒ processing, a maximum process temperature of only 450°C is allowed. The compatibility with the CMOS production process will become important because integration of light emitters is one of the major goals on the road map in semiconductor industries. This is because the performance of electronic integrated circuits is expected to be greatly increased by using optical signal transmission. 25 While the origins of the luminescence of porous silicon are still debated, the imperative of quantum confinement is generally accepted.26 Free Si clusters down to the size of a few atoms can be produced in molecular beam machines.17,27-31 A further and major requirement to achieve luminescence from Si is a suitable passivation of the surface.32 Pure free Si clusters exhibit dangling bonds that efficiently quench luminescence. 33 In this paper we report on a combination of the cluster beam approach and a passivation technique that overcomes this limitation. Central to this method is the in situ chemical interaction between the surface of pure silicon clusters and a passivation agent. The method yields luminescent clusters in aqueous suspensions immediately and the luminescence intensity remains stable over a period of more than three months. High temperature treatments ...

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“…As was suggested in [38], during the cooling of the jet prior to its injection into superfluid helium, nanoclusters of impurity particles with a higher freezing temperature are formed at first, and then impurity particles with a lower freezing temperature adsorb on the surface of the these nanoclusters. For example, in the supersonic jets containing rare gas atoms, clusters with multishell structures are formed [39][40][41][42]. In the case of nitrogen-neon samples, initially nanoclusters of molecular nitrogen which have the melting temperature close to that of molecular nitrogen matrix 2 N (Т = 63 K) form.…”

Section: Discussionmentioning

confidence: 99%

Dynamics of thermoluminescence spectra of impurity–helium condensates containing stabilized nitrogen and oxygen atoms

Khmelenko

Lee

Krushinskaya

et al. 2012

Low Temperature Physics

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The results of investigations of thermoluminescence dynamics during destruction of neon-helium and krypton-helium condensates containing stabilized nitrogen and oxygen atoms are presented. Spectra of the thermoluminescence of a krypton-helium condensate contained bands of N and O atoms and NO molecules. The intensities of the bands in these spectra were found to increase simultaneously during destruction processes in the temperature range 1.5-15 K. Observation of the NO molecules provides clear evidence for chemical reactions in the nanoclusters comprising the sample at low temperatures. Destruction of neon-helium samples occurred in two stages. During the first stage the α-group of N atoms surrounded by Ne and N 2 molecules dominated the spectra. During the second stage, the spectra contained intense bands of N and O atoms stabilized in a molecular nitrogen matrix. The unusual characteristics of the thermoluminescence spectra were observed, and their changes were explained in terms of the shell structure of impurity nanoclusters which comprised the impurity-helium condensates.

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Photochemical processes in doped argon-neon core-shell clusters: The effect of cage size on the dissociation of molecular oxygen

Cited by 12 publications

References 86 publications

A novel approach towards the production of luminescent silicon nanoparticles: sputtering, gas aggregation and co-deposition with H2O

A novel approach towards the production of luminescent silicon nanoparticles: sputtering, gas aggregation and co-deposition with H2O

In situ passivation and blue luminescence of silicon clusters using a cluster beam/H2O codeposition production method

Dynamics of thermoluminescence spectra of impurity–helium condensates containing stabilized nitrogen and oxygen atoms

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