Mechanism and energetics of dimerization of SiH2 radicals on H-terminated Si(001)-(2×1) surfaces

doi:10.1016/S0039-6028(03)00869-0

Surface Science

Volume 540, Issues 2–3, 20 August 2003, Pages L623-L630

https://doi.org/10.1016/S0039-6028(03)00869-0 Get rights and content

Abstract

The mechanism and energetics are presented of the dimerization of two adsorbed surface SiH₂ groups on the H-terminated Si(0 0 1)-(2 × 1) surface to form Si₂H₄ species during the initial stages of growth in plasma deposition of hydrogenated amorphous silicon (a-Si:H) films. The reactions are observed during classical molecular-dynamics (MD) simulations of a-Si:H film deposition from SiH₂ radical precursors impinging on an initially H-terminated Si(0 0 1)-(2 × 1) surface and substrate temperature, T, over the range 500⩽T⩽700 K. The Si₂H₄ species resulting from the surface SiH₂ dimerization reactions undergo surface conformational changes resulting in either a non-rotated (NRD) or a rotated dimer (RD) configuration. The RD configuration is found to be the energetically favorable one. The MD simulation results for the structure of the NRD and RD surface Si₂H₄ configurations corroborate with ab initio calculations of optimized adsorption configurations of SiH₂ radicals on crystalline Si surfaces, as well as results of STM imaging of the thermal decomposition of disilane on Si(0 0 1).

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Acknowledgements

This work was supported by the NSF/DoE Partnership for Basic Plasma Science and Engineering (Award nos. DMR-9713280 and ECS-0078711) and by the Camille and Henry Dreyfus Foundation through Camille Dreyfus Teacher-Scholar awards to two of the authors (E.S.A. and D.M.). Fruitful discussions with M.S. Valipa and S. Agarwal are gratefully acknowledged.

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The interest in disilene molecule comes from its intermediate role in the chemical vapor deposition of silicon [8], which is of particular importance for the silicon thin film growth for the future use in microelectronic devices. This molecule can be formed after dimerization of highly reactive [9] silylene (SiH2) radicals presented in a silane plasma [10] or, alternatively, upon direct dehydrogenization of disilane molecule [11], and will influence the final electronic properties of deposited material [10]. In addition, Maier et al. [5] have observed the formation of main Si2H4 isomers – disilene and silylsilylene – during the reaction of silicon atoms with silane molecules in a 10 K argon matrix and have shown that these isomers can be interconverted upon variation of the wavelength applied to matrices.
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Surface Science LettersMechanism and energetics of dimerization of SiH2 radicals on H-terminated Si(001)-(2×1) surfaces

Abstract

Section snippets

Acknowledgements

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Thin Solid Films

J. Non-Cryst. Solids

Surf. Sci.

Surf. Sci.

Surf. Sci.

Chem. Phys. Lett.

Chem. Phys. Lett.

J. Non-Cryst. Solids

Surf. Sci.

Phys. Status Solidi B

Appl. Phys. A

MRS Bull.

Science

J. Appl. Phys.

Appl. Phys. Lett.

J. Vac. Sci. Technol. A

J. Appl. Phys.

Surface Science Letters
Mechanism and energetics of dimerization of SiH₂ radicals on H-terminated Si( $0 0 1$ )-(2×1) surfaces