Theoretical study of the interactions of SiH2 radicals with silicon surfaces

Shyam Ramalingam, Pushpa Mahalingam, Eray Aydil, Dimitrios Maroudas

Research output: Contribution to journalArticle

Abstract

Silylene (SiH2) radicals created by electron impact dissociation of silane in reactive gas discharges can play an important role in plasma deposition of amorphous and nanocrystalline silicon thin films. In this article, we present a systematic computational analysis of the interactions of SiH2 radicals with a variety of crystalline and amorphous silicon surfaces based on atomistic simulations. The hydrogen coverage of the surface and, hence, the availability of surface dangling bonds is shown to exert the strongest influence on the radical-surface reaction mechanisms and the corresponding reaction probabilities. The SiH2 radical reacts with unit probability on the pristine Si(001)-(2×1) surface which has one dangling bond per Si atom; upon reaction, the Si atom of the radical forms strong Si-Si bonds with either one or two surface Si atoms. On the H-terminated Si(001)-(2×1) surface, the radical is found to react with a probability of approximately 50%. The SiH2 radical attaches itself to the surface either by forming two bonds with Si atoms of adjacent dimers in the same dimer row or through Si-Si bonds with one or both atoms of a surface dimer. In addition, the SiH2 radical can attach itself in the trough between dimer rows, forming two Si-Si bonds with second-layer Si atoms. The energetics and dynamics of these surface reactions are analyzed in detail. A reaction probability of approximately 70% is calculated for SiH2 radicals impinging on surfaces of hydrogenated amorphous silicon (a-Si:H) films with varying concentrations of hydrogen. Recent experimental measurements have reported a 60% loss probability for the SiH2 radical on the reactor walls through laser induced fluorescence. The experimentally obtained reaction probability falls within the range for the sticking coefficients on the H-terminated and amorphous film surfaces as determined by our atomistic calculations. Molecular-dynamics (MD) simulations of a-Si:H film growth by repeated impingement of SiH2 radicals have revealed adsorption reactions at early stages to occur with similar energetics as the corresponding reactions of isolated radicals on crystalline surfaces. The reaction probability of SiH2 on a-Si:H films deposited through MD simulations is approximately 30%. Finally, it is found that the SiH2 radical is much more mobile on surfaces of a-Si:H films than on crystalline surfaces, especially when the hydrogen concentration in the amorphous film and, thus, on the surface is high.

Original languageEnglish (US)
Pages (from-to)5497-5508
Number of pages12
JournalJournal of Applied Physics
Volume86
Issue number10
DOIs
StatePublished - Nov 15 1999

Fingerprint

silicon
interactions
dimers
amorphous silicon
atoms
surface reactions
hydrogen
molecular dynamics
simulation
impingement
gas discharges
troughs
silanes
laser induced fluorescence
electron impact
availability
reactors
dissociation
adsorption
coefficients

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Theoretical study of the interactions of SiH2 radicals with silicon surfaces. / Ramalingam, Shyam; Mahalingam, Pushpa; Aydil, Eray; Maroudas, Dimitrios.

In: Journal of Applied Physics, Vol. 86, No. 10, 15.11.1999, p. 5497-5508.

Research output: Contribution to journalArticle

Ramalingam, Shyam ; Mahalingam, Pushpa ; Aydil, Eray ; Maroudas, Dimitrios. / Theoretical study of the interactions of SiH2 radicals with silicon surfaces. In: Journal of Applied Physics. 1999 ; Vol. 86, No. 10. pp. 5497-5508.
@article{b871a3f6cfd14e94818eb26439b2bc48,
title = "Theoretical study of the interactions of SiH2 radicals with silicon surfaces",
abstract = "Silylene (SiH2) radicals created by electron impact dissociation of silane in reactive gas discharges can play an important role in plasma deposition of amorphous and nanocrystalline silicon thin films. In this article, we present a systematic computational analysis of the interactions of SiH2 radicals with a variety of crystalline and amorphous silicon surfaces based on atomistic simulations. The hydrogen coverage of the surface and, hence, the availability of surface dangling bonds is shown to exert the strongest influence on the radical-surface reaction mechanisms and the corresponding reaction probabilities. The SiH2 radical reacts with unit probability on the pristine Si(001)-(2×1) surface which has one dangling bond per Si atom; upon reaction, the Si atom of the radical forms strong Si-Si bonds with either one or two surface Si atoms. On the H-terminated Si(001)-(2×1) surface, the radical is found to react with a probability of approximately 50{\%}. The SiH2 radical attaches itself to the surface either by forming two bonds with Si atoms of adjacent dimers in the same dimer row or through Si-Si bonds with one or both atoms of a surface dimer. In addition, the SiH2 radical can attach itself in the trough between dimer rows, forming two Si-Si bonds with second-layer Si atoms. The energetics and dynamics of these surface reactions are analyzed in detail. A reaction probability of approximately 70{\%} is calculated for SiH2 radicals impinging on surfaces of hydrogenated amorphous silicon (a-Si:H) films with varying concentrations of hydrogen. Recent experimental measurements have reported a 60{\%} loss probability for the SiH2 radical on the reactor walls through laser induced fluorescence. The experimentally obtained reaction probability falls within the range for the sticking coefficients on the H-terminated and amorphous film surfaces as determined by our atomistic calculations. Molecular-dynamics (MD) simulations of a-Si:H film growth by repeated impingement of SiH2 radicals have revealed adsorption reactions at early stages to occur with similar energetics as the corresponding reactions of isolated radicals on crystalline surfaces. The reaction probability of SiH2 on a-Si:H films deposited through MD simulations is approximately 30{\%}. Finally, it is found that the SiH2 radical is much more mobile on surfaces of a-Si:H films than on crystalline surfaces, especially when the hydrogen concentration in the amorphous film and, thus, on the surface is high.",
author = "Shyam Ramalingam and Pushpa Mahalingam and Eray Aydil and Dimitrios Maroudas",
year = "1999",
month = "11",
day = "15",
doi = "10.1063/1.371552",
language = "English (US)",
volume = "86",
pages = "5497--5508",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "10",

}

TY - JOUR

T1 - Theoretical study of the interactions of SiH2 radicals with silicon surfaces

AU - Ramalingam, Shyam

AU - Mahalingam, Pushpa

AU - Aydil, Eray

AU - Maroudas, Dimitrios

PY - 1999/11/15

Y1 - 1999/11/15

N2 - Silylene (SiH2) radicals created by electron impact dissociation of silane in reactive gas discharges can play an important role in plasma deposition of amorphous and nanocrystalline silicon thin films. In this article, we present a systematic computational analysis of the interactions of SiH2 radicals with a variety of crystalline and amorphous silicon surfaces based on atomistic simulations. The hydrogen coverage of the surface and, hence, the availability of surface dangling bonds is shown to exert the strongest influence on the radical-surface reaction mechanisms and the corresponding reaction probabilities. The SiH2 radical reacts with unit probability on the pristine Si(001)-(2×1) surface which has one dangling bond per Si atom; upon reaction, the Si atom of the radical forms strong Si-Si bonds with either one or two surface Si atoms. On the H-terminated Si(001)-(2×1) surface, the radical is found to react with a probability of approximately 50%. The SiH2 radical attaches itself to the surface either by forming two bonds with Si atoms of adjacent dimers in the same dimer row or through Si-Si bonds with one or both atoms of a surface dimer. In addition, the SiH2 radical can attach itself in the trough between dimer rows, forming two Si-Si bonds with second-layer Si atoms. The energetics and dynamics of these surface reactions are analyzed in detail. A reaction probability of approximately 70% is calculated for SiH2 radicals impinging on surfaces of hydrogenated amorphous silicon (a-Si:H) films with varying concentrations of hydrogen. Recent experimental measurements have reported a 60% loss probability for the SiH2 radical on the reactor walls through laser induced fluorescence. The experimentally obtained reaction probability falls within the range for the sticking coefficients on the H-terminated and amorphous film surfaces as determined by our atomistic calculations. Molecular-dynamics (MD) simulations of a-Si:H film growth by repeated impingement of SiH2 radicals have revealed adsorption reactions at early stages to occur with similar energetics as the corresponding reactions of isolated radicals on crystalline surfaces. The reaction probability of SiH2 on a-Si:H films deposited through MD simulations is approximately 30%. Finally, it is found that the SiH2 radical is much more mobile on surfaces of a-Si:H films than on crystalline surfaces, especially when the hydrogen concentration in the amorphous film and, thus, on the surface is high.

AB - Silylene (SiH2) radicals created by electron impact dissociation of silane in reactive gas discharges can play an important role in plasma deposition of amorphous and nanocrystalline silicon thin films. In this article, we present a systematic computational analysis of the interactions of SiH2 radicals with a variety of crystalline and amorphous silicon surfaces based on atomistic simulations. The hydrogen coverage of the surface and, hence, the availability of surface dangling bonds is shown to exert the strongest influence on the radical-surface reaction mechanisms and the corresponding reaction probabilities. The SiH2 radical reacts with unit probability on the pristine Si(001)-(2×1) surface which has one dangling bond per Si atom; upon reaction, the Si atom of the radical forms strong Si-Si bonds with either one or two surface Si atoms. On the H-terminated Si(001)-(2×1) surface, the radical is found to react with a probability of approximately 50%. The SiH2 radical attaches itself to the surface either by forming two bonds with Si atoms of adjacent dimers in the same dimer row or through Si-Si bonds with one or both atoms of a surface dimer. In addition, the SiH2 radical can attach itself in the trough between dimer rows, forming two Si-Si bonds with second-layer Si atoms. The energetics and dynamics of these surface reactions are analyzed in detail. A reaction probability of approximately 70% is calculated for SiH2 radicals impinging on surfaces of hydrogenated amorphous silicon (a-Si:H) films with varying concentrations of hydrogen. Recent experimental measurements have reported a 60% loss probability for the SiH2 radical on the reactor walls through laser induced fluorescence. The experimentally obtained reaction probability falls within the range for the sticking coefficients on the H-terminated and amorphous film surfaces as determined by our atomistic calculations. Molecular-dynamics (MD) simulations of a-Si:H film growth by repeated impingement of SiH2 radicals have revealed adsorption reactions at early stages to occur with similar energetics as the corresponding reactions of isolated radicals on crystalline surfaces. The reaction probability of SiH2 on a-Si:H films deposited through MD simulations is approximately 30%. Finally, it is found that the SiH2 radical is much more mobile on surfaces of a-Si:H films than on crystalline surfaces, especially when the hydrogen concentration in the amorphous film and, thus, on the surface is high.

UR - http://www.scopus.com/inward/record.url?scp=0001108491&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001108491&partnerID=8YFLogxK

U2 - 10.1063/1.371552

DO - 10.1063/1.371552

M3 - Article

VL - 86

SP - 5497

EP - 5508

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

IS - 10

ER -