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Mechanism of hydrogen-induced crystallization of amorphous silicon

Abstract

Hydrogenated amorphous and nanocrystalline silicon films manufactured by plasma deposition techniques are used widely in electronic and optoelectronic devices1,2. The crystalline fraction and grain size of these films determines electronic and optical properties; the nanocrystal nucleation mechanism, which dictates the final film structure, is governed by the interactions between the hydrogen atoms of the plasma and the solid silicon matrix. Fundamental understanding of these interactions is important for optimizing the film structure and properties. Here we report the mechanism of hydrogen-induced crystallization of hydrogenated amorphous silicon films during post-deposition treatment with an H2 (or D2) plasma. Using molecular-dynamics simulations3,4 and infrared spectroscopy5, we show that crystallization is mediated by the insertion of H atoms into strained Si–Si bonds as the atoms diffuse through the film. This chemically driven mechanism may be operative in other covalently bonded materials, where the presence of hydrogen leads to disorder-to-order transitions.

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Figure 1: Simulated evolution of the Si–Si pair correlation function, g(r), of the a-Si:H film with increasing H exposure.
Figure 2: Simulated structural characteristics of Si film before and after H exposure.
Figure 3: Simulation and experimental evidence for the existence of the Si–H–Si (Si–D–Si) configuration.

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Acknowledgements

This work was supported by the NSF/DoE Partnership for Basic Plasma Science and Engineering and by the Camille and Henry Dreyfus Foundation through Camille Dreyfus Teacher-Scholar awards to E.S.A. and D.M.

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Correspondence to Eray S. Aydil or Dimitrios Maroudas.

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Sriraman, S., Agarwal, S., Aydil, E. et al. Mechanism of hydrogen-induced crystallization of amorphous silicon. Nature 418, 62–65 (2002). https://doi.org/10.1038/nature00866

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