Electronic states and total energies in hydrogenated amorphous silicon

Allan, Douglas C.; Joannopoulos, J. D.; Pollard, W. B.

doi:10.1103/physrevb.25.1065

Cited by 96 publications

(28 citation statements)

References 45 publications

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“…16 In this case, the lower activation energy of 1.90 eV was tentatively explained as arising from dihydride groups. This proposal agrees with theoretical calculations 15 indicating a lowering of the energy barrier when the H 2 molecule is formed. Within this model, the dissociation energy of the SiH group of process AЈ was determined from EGA experiments.…”

Section: ͑5͒supporting

confidence: 81%

“…Our results can be compared with several theoretical calculations of the energetics of various SiH groups 15,50 from which the dehydrogenation energy can be obtained if one assumes complete dangling-bond recombination and that hydrogen atoms recombine into a molecule. From the calculations of Allan et al 15 on a-Si: H, slight endothermic energies of −͑0.10-0.14͒ eV/͑H atoms͒ for the dehydrogenation of monohydride, dihydride, and neighboring SiH groups are obtained.…”

Section: B Enthalpy Of Dehydrogenation Of the Low-temperature Processesmentioning

confidence: 99%

“…From the calculations of Allan et al 15 on a-Si: H, slight endothermic energies of −͑0.10-0.14͒ eV/͑H atoms͒ for the dehydrogenation of monohydride, dihydride, and neighboring SiH groups are obtained. From those of Fedders, 50 we obtain −0.21 eV/͑H atoms͒ for weakly bonded hydrogen in clusters ͑from the analysis of Sec.…”

Section: B Enthalpy Of Dehydrogenation Of the Low-temperature Processesmentioning

confidence: 99%

“…They obtain an activation energy of 1.9 eV, consistent with independent experiments on the desorption of hydrogen from the surface of monocrystalline silicon 14 and with theoretical calculations. 15 This energy corresponds to the breaking of two neighboring SiH groups and the simultaneous formation of an H molecule. From this and other experimental evidence, it is known that this lowtemperature dehydrogenation process is usually associated with clustered SiH groups on the surface of internal voids.…”

Section: Introductionmentioning

confidence: 99%

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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: ͑5͒supporting

confidence: 81%

Section: B Enthalpy Of Dehydrogenation Of the Low-temperature Processesmentioning

confidence: 99%

Section: B Enthalpy Of Dehydrogenation Of the Low-temperature Processesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2006

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“…In (D) The ir-bond energy will be -59 kJ mol 1 the following sections we will first consider the This number is derived from the semi-empirical single-bound adsorbates, followed by the discusdata in ref. [22].…”

Section: Adsorption Enthalpiesmentioning

confidence: 99%

A theoretical study of adsorption equilibria in silicon CVD

Gardeniers

Giling

Jong

et al. 1990

Journal of Crystal Growth

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As part of a theoretical study of adsorption processes in the chemical vapour deposition of silicon, thermochemical data are derived for the adsorption of Si-H species on the Si(111) and the dimer-reconstructed Si(001)-(2 xl) surfaces. Essential contributions to the heats of adsorption appear to be electron pairing and two-and three-body interactions. It is shown that when the bond energies are defined in this way, also a consistent description of the bonds in silicon hydrides is provided. This demonstrates that with reasonable confidence the method can be applied to the adsorption process itself. Data are derived for species which may form one, two or even four bonds with the surface. It is assumed that on the (111) surface adsorbates bind on the "dangling bonds" which are present on this surface in a broken bond model. It is demonstrated that on the dimer reconstructed Si(001)-(2 xl) surface, adsorbates will either bind on the surface atoms with one or two bonds, without the breaking of the dimer bonds, or, if the species have the possibility to form two or four bonds with the surface atoms, may become inserted into the dimer bonds. With the aid of the derived thermochemical data for adsorption and the Langmuir isotherm or modifications thereof, the coverage of the Si(111) and the dimer reconstructed Si(001)-(2X1) surfaces with species from the Si-H system is calculated. It is found that the equilibrium surface coverages of the Si(111) and the Si(001)-(2 xl) surfaces are very similar: the hydrogen coverage is high at all temperatures, while at low supersaturation the coverage with growth species is very low on both surfaces.

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Electronic Structure of a‐SiH_x with Arbitrary Hydrogen Concentration

Wilke

Mašek

Velický

1986

Physica Status Solidi (b)

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The Bethe-lattice approach is used to describe the electronic structure of a-SiH, with arbitrary concentration of hydrogen. This is treated as a ternary alloy containing Si atoms, SiH and SiH, units interconnected randomly, or clustered. The tight-binding density of states is calculated for representative examples. Beside widening of the band gap, the local effects due to different hydrogen incorporation are obtained and discussed in terms of different, degree of localization of H-Si bonds.Die Bethe-Gitter-Naherung wird verwendet, um die Elektronenstruktur von a-SiH, mit beliebiger Wasserstoffkonzentration zu beschreiben. Dieses wird als ternares Mischsystem behandelt, das Si-Atome, SiH-und SiH,-Gruppen enthalt, die untereinander zufallig verbunden sind oder Cluster bilden. Die im ,,tight binding"-Model1 berechnete Zustandsdichte wird fur reprasentative Beispiele dargestellt. Neben der Erweiterung der Bandlucke werden die unterschiedlichem Wasserstoffeinbau entsprechenden lokslen Effekte erhalten und an Hand des verschiedenen Lokalisierungsgrades der H-Si Bindungen diskutiert.

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Electronic states and total energies in hydrogenated amorphous silicon

Cited by 96 publications

References 45 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

A theoretical study of adsorption equilibria in silicon CVD

Electronic Structure of a‐SiH_x with Arbitrary Hydrogen Concentration

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Electronic states and total energies in hydrogenated amorphous silicon

Cited by 96 publications

References 45 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

A theoretical study of adsorption equilibria in silicon CVD

Electronic Structure of a‐SiHx with Arbitrary Hydrogen Concentration

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Electronic Structure of a‐SiH_x with Arbitrary Hydrogen Concentration