Synthesis of Silicon Nanoclusters by Solid-Gas Reaction

Acker, Jörg; Bohmhammel, K.; Henneberg, E.; Irmer, G.; Röver, I.; Roewer, Gerhard

doi:10.1002/1521-4095(200011)12:21<1605::aid-adma1605>3.0.co;2-d

Cited by 16 publications

(11 citation statements)

References 6 publications

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“…As a rule of thumb, the free enthalpy of chloride formation must be less than -320 kJ mol -1 , as in the case of iron, cobalt, nickel, and copper (exact values for any metal and temperature can be calculated). 36 When the reaction conditions are mild, silicon is always present at or near the surface. The possibly formed nickel-chlorine bonds can be reduced by silicon, and chlorine is transferred from nickel to silicon by the same process.…”

Section: Solid-state Investigationsmentioning

confidence: 99%

“…It is assumed that electropositive hydrogenrich surface species (silylenoides) are more stable at low temperatures. 36 Furthermore, the increasing metal content of the solid phase (e.g., by silicon depletion) leads to an increase of the silicon tetrachloride yield (Figure 9). Hence, a higher number of chlorine adsorption sites are formed, and the chlorine concentration at the surface increases remarkably.…”

Section: Solid-state Investigationsmentioning

confidence: 99%

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Reactivity of Intermetallic Compounds: A Solid State Approach to Direct Reactions of Silicon

Acker

Bohmhammel

2002

J. Phys. Chem. B

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The present work is focused on a new approach to describe, quantify, and compare the reactivity of various transition metal silicide phases toward hydrogen chloride. Thermodynamic and kinetic parameters are obtained from isothermal calorimetric studies of these reactions. The reactivity of the silicide phases is discussed in terms of reaction start temperatures, rate constants, and apparent activation energies. Negative apparent activation energies are observed at low temperatures and are attributed to an initial stage of reaction where chlorine is chemisorbed and then incorporated into the silicide lattice near the surface. At a later time, a chlorine-containing reaction layer is formed having a composition and reactivity remarkably different from that of the bulk phase. On the basis of solid-state investigations, a diffusion model of the microscopic structure of these layers is presented, where a displacement of nickel atoms occurs followed by the occupation of nickel sites by chlorine. A model is suggested in which the electron level of the reaction layer is adjusted by the chlorine content of this layer, resulting in a electronic stabilization of silylenoide species at the surface. The model is applied to explain product distribution in the induction period during the direct reaction of silicon and methyl chloride.

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Section: Solid-state Investigationsmentioning

confidence: 99%

Section: Solid-state Investigationsmentioning

confidence: 99%

Reactivity of Intermetallic Compounds: A Solid State Approach to Direct Reactions of Silicon

Acker

Bohmhammel

2002

J. Phys. Chem. B

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“…6 A variety of techniques have been used to produce freestanding Si-NCs such as solid-gas reaction, 7 liquid phase synthesis, 8,9 laser pyrolysis of silane, [10][11][12][13] laser ablation, 14 , laser vaporizationcontrolled condensation, 15 and plasma-assisted decomposition of silane. 1,6,16,17 Amongst these, the latter silane plasma method has proved to be very efficient in producing large quantities of high quality Si-NCs passivated with Si-H bonds (silane plasma Si-NCs) with control over diameter in the range 3-50 nm.…”

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confidence: 99%

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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“…Freestanding Si-NCs can be fabricated by various techniques, including solid-gasreaction, 10 liquid-phase synthesis, 11,12 laser pyrolysis of silane, 13,14 laser ablation, 15 laser vaporization-controlled condensation, 16 and plasma-assisted decomposition of silane. 1,2,17,18 Several recent experimental investigations have focused on fundamental characteristics of these SiNCs such as light emission, 2,3 electronic doping, 19,20 and optical properties.…”

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confidence: 99%

Freestanding silicon nanocrystals with extremely low defect content

et al. 2012

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The future exploitation of the exceptional properties of freestanding silicon nanocrystals (Si-NCs) in marketable applications relies upon our ability to produce large amounts of defect-free Si-NCs by means of a low-cost method. Here, we demonstrate that Si-NCs fabricated by scalable RF plasmaassisted decomposition of silane with additional hydrogen gas injected into the afterglow region of the plasma exhibit immediately after synthesis the lowest reported defect density, corresponding to a value of only about 0.002-0.005 defects per NC for Si-NCs with 4 nm in size. In addition, the virtually perfect hydrogen termination of these Si-NCs yields an enhanced resistance against natural oxidation in comparison to Si-NCs with nearly one order of magnitude larger initial defect density.

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Synthesis of Silicon Nanoclusters by Solid-Gas Reaction

Cited by 16 publications

References 6 publications

Reactivity of Intermetallic Compounds: A Solid State Approach to Direct Reactions of Silicon

Reactivity of Intermetallic Compounds: A Solid State Approach to Direct Reactions of Silicon

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

Freestanding silicon nanocrystals with extremely low defect content

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