Nuclear magnetic resonance investigation of H, H2 and dopants in hydrogenated amorphous silicon and related materials

Boyce, J. B.; Ready, S. E.

doi:10.1016/0921-4526(91)90142-2

Cited by 33 publications

(9 citation statements)

References 37 publications

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“…7 Their concentration was measured after isothermal annealing, and it was shown to increase at the temperatures where the main SiH groups began to dissociate. 54 However, one cannot say properly that, in those experiments, the H 2 molecules were effectively trapped. Their detection could simply indicate the delay between SiH dissociation and hydrogen evolution which is evident in our experiments from the delay between the DSC and EGA peaks.…”

Section: H 2 Trapped In Conventional A-si: H and The Real Values Ofmentioning

confidence: 99%

Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

et al. 2006

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Differential scanning calorimetry ͑DSC͒ was used to study the dehydrogenation processes that take place in three hydrogenated amorphous silicon materials: nanoparticles, polymorphous silicon, and conventional device-quality amorphous silicon. Comparison of DSC thermograms with evolved gas analysis ͑EGA͒ has led to the identification of four dehydrogenation processes arising from polymeric chains ͑A͒, SiH groups at the surfaces of internal voids ͑AЈ͒, SiH groups at interfaces ͑B͒, and in the bulk ͑C͒. All of them are slightly exothermic with enthalpies below 50 meV/͑H atoms͒, indicating that, after dissociation of any SiH group, most dangling bonds recombine. The kinetics of the three low-temperature processes ͓with DSC peak temperatures at around 320 ͑A͒, 360 ͑AЈ͒, and 430°C ͑B͔͒ exhibit a kinetic-compensation effect characterized by a linear relationship between the activation entropy and enthalpy, which constitutes their signature. Their Siu H bond-dissociation energies have been determined to be E͑Siu H͒ 0 = 3.14 ͑A͒, 3.19 ͑AЈ͒, and 3.28 eV ͑B͒. In these cases it was possible to extract the formation energy E͑DB͒ of the dangling bonds that recombine after Siu H bond breaking ͓0.97 ͑A͒, 1.05 ͑AЈ͒, and 1.12 ͑B͔͒. It is concluded that E͑DB͒ increases with the degree of confinement and that E͑DB͒ Ͼ 1.10 eV for the isolated dangling bond in the bulk. After Siu H dissociation and for the low-temperature processes, hydrogen is transported in molecular form and a low relaxation of the silicon network is promoted. This is in contrast to the high-temperature process for which the diffusion of H in atomic form induces a substantial lattice relaxation that, for the conventional amorphous sample, releases energy of around 600 meV per H atom. It is argued that the density of sites in the Si network for H trapping diminishes during atomic diffusion.

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Section: H 2 Trapped In Conventional A-si: H and The Real Values Ofmentioning

confidence: 99%

Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

et al. 2006

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“…In addition, for reasonable choices of ∆ω and τ 0 the observed values of T 1 imply that the doublet lineshape should be motionally narrowed, which is also not the case. Earlier works have suggested that if there exists a distribution of τ, which is very likely in disordered materials, then one might be able to fit the observed temperature dependence of T 1 consistently [5,6]; however, even if this is the case, the observed lineshape will be a sum of the line shapes with hydrogen atoms at different sites, and one would again expect a change in lineshape with temperature. Therefore, if the hydrogen pairs are undergoing local motion, it must be some form of correlated motion that maintains the distance between the two hydrogen atoms in a pair.…”

Section: The Hydrogen Doublet Defectmentioning

confidence: 78%

Innovative Characterization of Amorphous and Thin-Film Silicon for Improved Module Performance: 1 February 2005 - 31 July 2008

Taylor¹,

Williams²

2009

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“…Nevertheless, aerosol particles differ noticeably from a-Si:H films. For example, the bonded hydrogen in a-Si:H films is mainly SiH groups embedded in amorphous silicon network in vacancies and hydrogen complexes [46][47][48][49][50][51][52][53][54][55]. As to particles, the high fraction of bonded hydrogen is localized on the surface of interconnected microvoids and microchannels [43,45].…”

Section: Introductionmentioning

confidence: 99%

“…The hydrogen of both SiH groups with 2000 cm -' frequency and polyhydride groups gives a broad NMR line (25 kHz) due to homonuclear dipole interaction [43]. Relatively to NMR this hydrogen resides in a clustered environment [47][48][49][50]. Therefore, SiH groups with 2000 cm -' frequency are called "clustered" monohydride groups.…”

Section: Introductionmentioning

confidence: 99%

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EPR investigation of a-Si:H aerosol particles formed under silane thermal decomposition

et al. 1998

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The dangling bond defects were investigated in a-Si:H particles formed under silane thermal decomposition in flow reactor. EPR together with hydrogen evolution method were used. The experimental results allowed us to conclude that there are two kinds of dangling bond defects in aSi:H aerosol particles. The defects of the first kind are localized on the surface of interconnected microvoids and microchannels (surface dangling bonds) and those of the second kind are embedded in amorphous silicon network (volume dangling bonds). The thermal equilibration of dangling bonds and temperature dependence of equilibrium dangling bond concentration were investigated. It was found that at temperatures >400 K the dangling bond concentration N reversibly depends on sample temperature. The volume dangling bond concentration increases with temperature increasing (the effective activation energy of dangling bond formation U> 0), and the surface dangling bond concentration decreases with temperature increasing (U < 0). It has been found that EPR line is considerably asymmetric for samples with high hydrogen content and for low hydrogen content the EPR line is weakly asymmetric. A conclusion was drawn that the asymmetry degree depends on amorphous silicon lattice distortions. This conclusion has been confirmed by EPR spectra simulations.

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Nuclear magnetic resonance investigation of H, H2 and dopants in hydrogenated amorphous silicon and related materials

Cited by 33 publications

References 37 publications

Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

Innovative Characterization of Amorphous and Thin-Film Silicon for Improved Module Performance: 1 February 2005 - 31 July 2008

EPR investigation of a-Si:H aerosol particles formed under silane thermal decomposition

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