Dense restructuring of amorphous silicon network induced by non-bonded hydrogen

Sekimoto, Takeyuki; Matsumoto, Mitsuhiro; Terakawa, Akira

doi:10.7567/jjap.57.08rb07

Cited by 6 publications

(15 citation statements)

References 87 publications

(222 reference statements)

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“…This parameter is associated with the atomic coordinance average number, so its decrease suggests more vacancies are introduced in the tissue . This result agrees with the findings reported by Sekimoto et al, which revealed the aggregation of vacancies driven by the hydrogen molecules trapped within …”

Section: Discussionsupporting

confidence: 92%

“…This porosity seems to increase further, as the static index decreases to around 2.7, as a result of the H 2 treatment, in agreement with the ellipsometry results. This result is in line with the suggestion that hydrogen molecules in the film lead to the creation of nanovoids, as proposed in the study of Sekimoto et al and Sekimoto, Matsumoto, and Terakawa . Moreover, E w is decreased from 27 to 21 eV.…”

Section: Discussionsupporting

confidence: 91%

“…Since the I 2000 / I 2090 ratio was found to decrease as a result of the H 2 treatment, one could infer that there is an increase in the number of nanovoids. This agrees with the model proposed by Sekimoto et al, which proposes that hydrogen molecules trapped around vacancies exert a compressive stress, which induce the vacancies to agglomerate and create larger vacancies (voids) . The authors also predict that a structural modification, meaning a change from small vacancies to larger nanovoids, should be accompanied with a change in the optical gap of the films.…”

Section: Discussionsupporting

confidence: 88%

“…The formation of both the Si‐SiH 3 network and the increase in the porosity indicates that the microstructure of the films was radically modified as a result of the H 2 treatment. A detailed microstructural study of the effect of hydrogen molecules on the structure of a‐Si:H films was recently published, where it was suggested that hydrogen molecules trapped in small vacancies, meaning small pockets of structural inhomogeneity where one or two silicon atoms are missing, increases the number of larger voids, thus relaxing internal stresses in the material . Indeed, it has been observed that in porous a‐Si:H structures, hydrogen molecules are often trapped in nano‐sized voids .…”

Section: Discussionmentioning

confidence: 99%

See 3 more Smart Citations

Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Filali

Brahmi

Sib

et al. 2019

Surface & Interface Analysis

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Highly crystallized hydrogenated silicon layers were obtained via the treatment of hydrogenated polymorphous silicon films in a molecular hydrogen ambient. This contrasts other postdeposition studies that obtained nanocrystalline silicon films but necessitated either a plasma activation or high-temperature annealing. The structure of the samples was analyzed by Raman spectroscopy to determine the crystallite volume fraction, which was found to increase up to 80% within 1 hour of treatment.Atomic force microscopy (AFM) showed that the roughness of the surfaces was found to increase after the H 2 treatment. Optical transmission and spectroscopic ellipsometry revealed the pronounced porosity of the films characterized by a static refractive index that is below three, which is a low value for hydrogenated silicon films and a void fraction that is around 15% in the bulk of the films. The effect of the hydrogen molecules on the structure of the films was discussed in terms of the compressive stress exerted by the molecules, trapped in structural inhomogeneities, on the amorphous tissue. It is suggested that for this process to take effect, the films need to be porous and that the amorphous network needs to be in a "relaxed" state.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Filali

Brahmi

Sib

et al. 2019

Surface & Interface Analysis

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“…Experimental data from positron-annihilation lifetime (PAL) spectroscopy, 13 Rutherford backscattering spectrometry (RBS), 59 and Fourier-transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) 59 This value matches very well with the experimental value of 10 21 H 2 /cm 3 from IR measurements by Chabal and Patel, 24 as mentioned earlier. These results are also consistent with the reported data from RBS measurements.…”

Section: Silicon-hydrogen Bonding Configurations On Void Surfacessupporting

confidence: 75%

Temperature-induced nanostructural evolution of hydrogen-rich voids in amorphous silicon: a first-principles study

et al. 2020

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The paper presents an ab initio study of temperature-induced nanostructural evolution of hydrogen-rich voids in amorphous silicon. By using ultra-large a-Si models, obtained from classical molecular-dynamics simulations, with a realistic void-volume density of 0.2%, the dynamics of Si and H atoms on the surface of the nanometer-size cavities were studied and their effects on the shape and size of the voids were examined using first-principles density-functional simulations. The results from ab initio calculations were compared with those obtained from using the modified Stillinger-Weber potential. The temperature-induced nanostructural evolution of the voids was examined by analyzing the three-dimensional distribution of Si and H atoms on/near void surfaces using the convex-hull approximation, and computing the radius of gyration of the corresponding convex hulls. A comparison of the results with those from the simulated values of the intensity in small-angle X-ray scattering of a-Si/a-Si:H in the Guinier approximation is also provided, along with a discussion on the dynamics of bonded and non-bonded hydrogen in the vicinity of voids.

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Ab Initio Hydrogen Dynamics and the Morphology of Voids in Amorphous Silicon

Biswas

Limbu

2021

Physica Status Solidi (b)

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This article presents an ab initio study of hydrogen dynamics inside nanometer‐size voids in amorphous silicon (a‐Si) within the framework of the density‐functional theory for a varying hydrogen load of 10–30 atoms per void at the low and high temperature of 400 and 700 K, respectively. Using the local density approximation (LDA) and its generalized‐gradient counterpart (GGA), the dynamics of hydrogen atoms inside the voids are examined with an emphasis on the diffusion of H atoms/molecules, and the resulting nanostructural changes of the void surfaces. The results from simulations suggest that the microstructure of the hydrogen distribution on the void surfaces and the morphology of the voids are characterized by the presence of a significant number of monohydride SiH bonds, along with a few dihydride SinormalH2 configurations. The study also reveals that a considerable number (about 10–45 at%) of total H atoms inside a void can appear as H2 molecules for a hydrogen load of 10–30 H atoms per void. The approximate shape of the voids is addressed from a knowledge of the positions of the void‐surface atoms using the convex‐hull approximation and the Gaussian broadening of the pseudoatomic surfaces of Si and H atoms.

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Dense restructuring of amorphous silicon network induced by non-bonded hydrogen

Cited by 6 publications

References 87 publications

Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Molecular hydrogen‐induced nucleation of hydrogenated silicon nanocrystals at low temperature

Temperature-induced nanostructural evolution of hydrogen-rich voids in amorphous silicon: a first-principles study

Ab Initio Hydrogen Dynamics and the Morphology of Voids in Amorphous Silicon

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