Abstraction of hydrogen by SiH radicals from hydrogenated amorphous silicon surfaces

The dynamics and energetics are presented of two Eley-Rideal reactions by w hich SiH radicals impinging at thermal energies on growth surfaces during p lasma deposition of hydrogenated amorphous silicon (a-Si:H) films abstract hydrogen atoms from the surface and return to the gas phase as SiH2 radical s. The reactions were observed during classical molecular-dynamics simulati ons of a-Si:H film deposition from SiH radicals impinging on an initially H -terminated Si(001)-(2 x 1) surface maintained at 500 K. The H-abstraction reaction may either produce a dangling bond on the surface or eliminate a s urface coordination defect. The computed activation energy barriers for the two hydrogen abstraction reactions are 0.15 and 0.07 eV, respectively, and the corresponding exothermic reaction energies are 0.20 and 0.30 eV. The e ffects of both reactions on the growth surface are examined through detaile d analysis involving the local structural configurations and the associated bond angle and bond length distributions in the vicinity of the surface hy drogen abstraction sites. (C) 2000 Elsevier Science B.V. All rights reserve d.