The mechanism and energetics are presented of the dimerization of two adsorbed surface SiH2 groups on the H-terminated Si(001)-(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(001)-(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(001).
Bibliographical noteFunding Information:
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.
Copyright 2008 Elsevier B.V., All rights reserved.
- Hydrogen atom
- Molecular dynamics
- Plasma processing
- Semiconductor-semiconductor thin film structures
- Surface chemical reaction