A model structure for hydrogenated amorphous silicon

Weaire, D.; Higgins, N. A.; Moore, Peter B.; Marshall, I.

doi:10.1080/13642817908246374

Cited by 35 publications

(8 citation statements)

References 5 publications

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“…The Si-D, Si-H, Si-F and Si-Si bond lengths, r i j , were investigated by fitting the relevant peaks in T (r ) (figures 14 and 15), and the values obtained are summarized in table 3, together with the root mean square (rms) bond length variations, (u 2 i j ) 1/2 , and the coordination numbers, n i( j ) , where appropriate. As may be seen from the later figures 25 and 27 showing the component correlation functions for the structural models of Weaire et al [55,56] and Winer and Wooten [58], there is a problem in fitting for the Si-Si bond length in that both Si-H and H-H interactions extend under the Si-Si peak. For this reason n Si(Si) was initially fixed at the value given by equation ( 9), and a fit was performed to the low-r side of the peak.…”

Section: Diffractionmentioning

confidence: 96%

“…Structural models of the network component of hydrogenated amorphous silicon have been published by Weaire et al [55,56], Guttman [57] and Winer and Wooten [58]. The Weaire et al model is in the form of an approximately spherical cluster, comprising a total of 397 atoms (314 Si and 83 H), while that of Winer and Wooten has been generated with a periodic boundary.…”

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confidence: 99%

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Neutron scattering studies of hydrogenated, deuterated and fluorinated amorphous silicon

Wright

Hannon

Sinclair

et al. 2007

J. Phys.: Condens. Matter

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A comprehensive neutron scattering study has been performed of hydrogenated (SiH), deuterated (SiD) and partially fluorinated deuterated (SiDF) amorphous silicon, prepared by the glow-discharge technique. The measurements performed include diffraction, small-angle neutron scattering (SANS) and inelastic neutron scattering, and the data obtained are discussed in terms of various structural models in the literature. The real-space correlation function for SiD exhibits sharp peaks at 1.49 and 2.36 Å, due to Si-D and Si-Si covalent bonds, respectively, while peaks centred at 3.2 and 3.8 Å are due to Si-D and Si-Si second-neighbour distances. High-energy resolution inelastic scattering measurements for SiH show that there are approximately equal numbers of [Formula: see text] and = SiH groupings, there being no indication of excitations corresponding to -SiH groupings. The presence of molecular hydrogen is demonstrated unambiguously by the observation of the ortho-to-para conversion, via molecular rotation modes at 14.5 and 29.4 meV. The shift in the Si-H stretch modes introduced by deuteration is slightly less than the value of [Formula: see text] expected for free hydrogen, indicating a small but observable influence of the amorphous silicon matrix. The size of the cages containing the H molecules has been investigated via SANS, which yields a mean Guinier radius of ∼5-6 Å. In addition, the use of the H-D SANS contrast technique indicates that each cage contains on average about 60 H (D) molecules. The data for the SiDF sample are consistent with a previously suggested model of network cages predominantly containing molecular SiF.

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Section: Diffractionmentioning

confidence: 96%

mentioning

confidence: 99%

Neutron scattering studies of hydrogenated, deuterated and fluorinated amorphous silicon

Wright

Hannon

Sinclair

et al. 2007

J. Phys.: Condens. Matter

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“…7,40,42 Normally, a sphere of 1 nm radius in a-Si:H (Si densityϷ5ϫ10 22 atoms/cm Ϫ3 ) contains more than 150 Si atoms. 43 Thus, the PL electrons are considered to have substantial electron densities on several dozen Si atoms and therefore do not adopt the same 29 Si hf interactions as the 2.004 electrons.…”

Section: B Comparison Between Lesr Centers and Other Band-tail Statesmentioning

confidence: 99%

Microscopic origin of light-induced ESR centers in undoped hydrogenated amorphous silicon

Umeda

Yamasaki²,

Isoya

et al. 2000

Phys. Rev. B

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29 Si hyperfine ͑hf͒ structures of light-induced electron-spin-resonance ͑LESR͒ centers of gϭ2.004 and 2.01 have been investigated in undoped hydrogenated amorphous silicon (a-Si:H) with different 29 Si content ͑1.6, 4.7,9.1 at. %͒ by means of pulsed and multifrequency ͑3,11,34 GHz͒ ESR techniques. We have experimentally deconvoluted overlapping LESR signals using the difference in the spin-lattice relaxation time between the two signals. The deconvoluted 29 Si hf structure of gϭ2.004 indicates that the wave function of the gϭ2.004 center spreads mainly over two Si atoms. Accordingly, we propose that the origin of gϭ2.004 is electrons trapped in antibonding states of weak Si-Si bonds rather than those trapped at positively charged dangling bonds. The isotropic hf splittings were estimated to be around 7 mT for gϭ2.004 and below 3 mT for gϭ2.01, which are in good agreement with characteristics of the antibonding and bonding states of the weak Si-Si bond. We suggest, from our 29 Si hf data and other experimental findings, that the gϭ2.004 center is localized spatially more than conduction-band-tail electrons detected by photoluminescence.

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“…The authors of [16] speculated about the nature of the high frequency stretching mode in Ge : H. They suggested as a possibility clusters of two second-nearest-neighbour Ge atoms each bonded to one H and with the Ge-H bonds pointing towards a Ge vacancy. I n the meantime models for hydrogenated a-Ge and a-Si:H have been built [20]. We show in Fig.…”

Section: Stretching Bands At 2100 Cm-imentioning

confidence: 99%

Infrared Spectrum and Structure of Hydrogenated Amorphous Silicon

Shanks

Fang

Ley

et al. 1980

Physica Status Solidi (b)

515

131

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The ir absorption spectrum of hydrogenated amorphous silicon is discussed in the context of structural models for this material. It is shown that the integrated strength of the bond stretching bands in hydrogenated amorphous silicon cannot be used to determine the hydrogen concentration because the local effective charge for ir absorption is a function of hydrogen concentration and sample preparation. The effective charge for the wagging-rocking-rolling vibrations a t 640 cm-', however, is independent of hydrogen concentration and sample preparation. Hence the integrated strength of this band can be used to measure the hydrogen concentration provided the proportionality constant is determined empirically. Changes in the ir absorption bands as a function of isochronal annealing temperature show that two different types of bonds contribute t o the bond stretching band a t 2100 cm-l. The bond bending bands a t 890 and 840 cm-1 are associated with one of the bonds producing the 2100 cm-' stretching band. The relative strengths of the 890 and 840 cm-1 bands to the 2100 cm-l band depend strongly on the film preparation method: the glow discharge produced films show much stronger bending bands than those produced by r f sputtering. A structural model for hydrogenated amorphous silicon is presented in which a Maxwell-Garnetttype local field correction, which is dependent on the dipole location within a microvoid and the shape of the microvoid, is used to explain the data.Das IR-Absorptionsspektrum von hydrogenisiertem, amorphem Silizium wird im Zusammenhang mit Strukturmodellen fiir dieses Naterial untersucht. Es wird gezeigt, daB die integrale Starke der ,,bond-stretching"-Banden in hydrogenisiertem, amorphem Silizium nicht fur die Bestimmung der Wasserstoffkonzentration benutzt werden kann, weil die lokale effektive Ladung fur die IR-Absorption eine Funktion der Wasserstoffkonzentration und Probenpraparation ist. Die effektive Ladung fur die ,,wagging-rocking-rolling"-Schwingungen bei 640 cm-l ist jedoch unabhingig von der Wasserstoffkonzentration und Probenpraparation. Somit kann die integrale Starke dieser Bande benutzt werden, um die Wasserstoffkonzentrtion zu messen, vorausgesetzt, daB die Proportionalitatskonstante empirisch bestimmt wird. Anderungen in den IR-Absorptionsbanden in Abhangigkeit von der isochronen Temperungstemperatnr zeigen, daB zwei unterschiedliche Bindungsarten zur ,,bond-stretching"-Bande bei 2100 cm-1 beitragen. Die ,,bond-bending"-Banden bei 890 und 840 cm-l sind mit einer der Bindungen verknupft, die die 2100 cm-'-Stretching-Bande hervorrufen. Die relativen Starken der 890-und 840-cm-l-Banden zur 2100 cm-l-Bande hangen stark von der Schichtherstellungsmethode ab : die durch Glimmentladung hergestellten Schichten zeigen vie1 starkere Bindungsbanden als die durch HF-Sputtern hergestellten. Ein Strukturmodell fur hydrogenisiertes, amorphes Silizium wird angegeben, in dem eine lokale Feldkorrektur vom Maxwell-Garnett-Typ benutzt wird, die von der Dipollokalisierung im Innern eines Mikrohohlraume...

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A model structure for hydrogenated amorphous silicon

Cited by 35 publications

References 5 publications

Neutron scattering studies of hydrogenated, deuterated and fluorinated amorphous silicon

Neutron scattering studies of hydrogenated, deuterated and fluorinated amorphous silicon

Microscopic origin of light-induced ESR centers in undoped hydrogenated amorphous silicon

Infrared Spectrum and Structure of Hydrogenated Amorphous Silicon

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