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An Electron Microscopy Study of the effects of Deposition Conditions on the Growth of Glow Discharge Prepared a-Ge:H Films.

Published online by Cambridge University Press:  25 February 2011

Scott J. Jones ,
Warren A. Turner ,
Dawen Pang  and
William Paul
Scott J. Jones
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138.
Warren A. Turner
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138.
Dawen Pang
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138.
William Paul
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138.
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Abstract

Electron microscopy techniques have been used to study the effect of deposition conditions on island growth and coalescence in r.f. glow discharge prepared a-Ge:H. Planar views of 500 Å thick films were obtained using transmission electron microscopy (TEM) while scanning electron microscopy (SEM) was used to investigate the cross-sectional microstructure of thicker films. Films were prepared on both electrodes of a capacitively-coupled, diode deposition system. The substrate temperature, level of applied power, externally applied d.c. substrate bias, and the germane to diluent gas ratio were systematically varied. For films prepared on the unpowered electrode, island coalescence was dramatically enhanced with increasing substrate temperature while columnar structure, found for samples prepared at lower substrate temperatures, vanished. Both effects are attributed to the elimination of a coalescence barrier with increased temperature. Increasing negative substrate bias slightly increased island coalescence while increasing the level of applied power had no visible effect on film microstructure. The island size decreased with increasing dilution of the gas plasma by H2. The addition of GeF4 to the gas plasma leads to a low density, porous film. This observation is attributed to either a difference in the plasma chemistry or increased film etching due to the presence of F in the gas plasma. High quality films prepared on the powered electrode were found to be more structurally homogeneous and environmentally stable than films prepared on the unpowered electrode at the same substrate temperature. Enhanced bombardment and/or a different plasma chemistry near the powered electrode are two factors which may contribute to the observed difference in microstructure.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 202: Symposium C – Evolution of Thin Film and Surface Microstructure , 1990 , 43
Copyright
Copyright © Materials Research Society 1991

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References

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