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Issue 29, 2009
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Rapid, low-temperature synthesis of nc-Si in high-density, non-equilibrium plasmas: enabling nanocrystallinity at very low hydrogen dilution

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Abstract

Nanocrystalline silicon thin films were deposited on single-crystal silicon and glass substrates simultaneously by inductively coupled plasma-assisted chemical vapor deposition from the reactive silane reactant gas diluted with hydrogen at a substrate temperature of 200 °C. The effect of hydrogen dilution ratio X (X is defined as the flow rate ratio of hydrogen to silane gas), ranging from 1 to 20, on the structural and optical properties of the deposited films, is extensively investigated by Raman spectroscopy, X-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/VIS spectroscopy, and scanning electron microscopy. Our experimental results reveal that, with the increase of the hydrogen dilution ratio X, the deposition rate Rd and hydrogen content CH are reduced while the crystalline fraction Fc, mean grain size δ and optical bandgap ETauc are increased. In comparison with other plasma enhanced chemical vapor deposition methods of nanocrystalline silicon films where a very high hydrogen dilution ratio X is routinely required (e.g. X > 16), we have achieved nanocrystalline silicon films at a very low hydrogen dilution ratio of 1, featuring a high deposition rate of 1.57 nm/s, a high crystalline fraction of 67.1%, a very low hydrogen content of 4.4 at.%, an optical bandgap of 1.89 eV, and an almost vertically aligned columnar structure with a mean grain size of approximately 19 nm. We have also shown that a sufficient amount of atomic hydrogen on the growth surface essential for the formation of nanocrystalline silicon is obtained through highly-effective dissociation of silane and hydrogen molecules in the high-density inductively coupled plasmas.

Graphical abstract: Rapid, low-temperature synthesis of nc-Si in high-density, non-equilibrium plasmas: enabling nanocrystallinity at very low hydrogen dilution

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Publication details

The article was received on 02 Mar 2009, accepted on 28 Apr 2009 and first published on 29 May 2009


Article type: Paper
DOI: 10.1039/B904227J
Citation: J. Mater. Chem., 2009,19, 5134-5140
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    Rapid, low-temperature synthesis of nc-Si in high-density, non-equilibrium plasmas: enabling nanocrystallinity at very low hydrogen dilution

    Q. Cheng, S. Xu and K. (. Ostrikov, J. Mater. Chem., 2009, 19, 5134
    DOI: 10.1039/B904227J

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