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Sub-Surface Equilibration of Hydrogen with the a-Si:H Network Under Film Growth Conditions

Published online by Cambridge University Press:  01 January 1993

ILSIN An ,
Y.M. Li ,
C.R. Wronski  and
R. W. Collins
ILSIN An
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
Y.M. Li
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
C.R. Wronski
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
R. W. Collins
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
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Abstract

In this study we characterize hydrogen diffusion and reaction processes in the near-surface (top 200 Å) of a-Si:H that lead to network equilibration under standard conditions of plasma-enhanced chemical vapor deposition (PECVD). Real time spectroscopic ellipsometry (SE) is used to provide continuous kinetic information on the near-surface conversion of Si-Si to Si-H bonds during exposure of in situ-prepared films at 250°C to filament-generated atomic H. We have found that for optimum PECVD a-Si:H, the formation of additional Si-H bonds is limited by the capture of H at trapping sites, and the rapid diffusion process (D>10-14 cm2/s) by which H reaches the site is not detected optically. Deep trapping occurs at a rate of ∼10 3 s-1 under our filament conditions, estimated to generate ∼1020 cm-3 mobile H in the near-surface of the film. Finally, more than 1021 cm-3 additional H atoms are trapped with emission rates <2×10-7 s-1, suggesting trap depths >2.0 eV. Shallower traps are also detected at lower concentration.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 297: Symposium A – Amorphous Silicon Technology - 1993 , 1993 , 43
Copyright
Copyright © Materials Research Society 1993

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References

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