Structural origins of intrinsic stress in amorphous silicon thin films

Eric Johlin, Nouar Tabet, Sebastián Castro-Galnares, Amir Abdallah, Mariana I. Bertoni, Tesleem Asafa, Jeffrey C. Grossman, Syed Said, Tonio Buonassisi

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Abstract

Hydrogenated amorphous silicon (a-Si:H) refers to a broad class of atomic configurations, sharing a lack of long-range order, but varying significantly in material properties, including optical constants, porosity, hydrogen content, and intrinsic stress. It has long been known that deposition conditions affect microstructure, but much work remains to uncover the correlation between these parameters and their influence on electrical, mechanical, and optical properties critical for high-performance a-Si:H photovoltaic devices. We synthesize and augment several previous models of deposition phenomena and ion bombardment, developing a refined model correlating plasma-enhanced chemical vapor deposition conditions (pressure and discharge power and frequency) to the development of intrinsic stress in thin films. As predicted by the model presented herein, we observe that film compressive stress varies nearly linearly with bombarding ion momentum and with a (-1/4) power dependence on deposition pressure, that tensile stress is proportional to a reduction in film porosity, and the net film intrinsic stress results from a balance between these two forces. We observe the hydrogen-bonding configuration to evolve with increasing ion momentum, shifting from a void-dominated configuration to a silicon-monohydride configuration. Through this enhanced understanding of the structure-property-process relation of a-Si:H films, improved tunability of optical, mechanical, structural, and electronic properties should be achievable.

Original languageEnglish
Article number075202
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume85
Issue number7
DOIs
Publication statusPublished - 6 Feb 2012
Externally publishedYes

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ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Johlin, E., Tabet, N., Castro-Galnares, S., Abdallah, A., Bertoni, M. I., Asafa, T., Grossman, J. C., Said, S., & Buonassisi, T. (2012). Structural origins of intrinsic stress in amorphous silicon thin films. Physical Review B - Condensed Matter and Materials Physics, 85(7), [075202]. https://doi.org/10.1103/PhysRevB.85.075202