Motility of Metal Nanoparticles in Silicon and Induced Anisotropic Silicon Etching

Authors

  • Kuiqing Peng,

    Corresponding author
    1. Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science City University of Hong Kong Hong Kong SAR (P. R. China)
    2. Department of Materials Science and Engineering Institute of Low Energy Nuclear Science Beijing Normal University, Beijing, 100875 (P. R. China)
    • Department of Materials Science and Engineering Institute of Low Energy Nuclear Science Beijing Normal University, Beijing, 100875 (P. R. China).
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  • Aijiang Lu,

    1. Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science City University of Hong Kong Hong Kong SAR (P. R. China)
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  • Ruiqin Zhang,

    1. Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science City University of Hong Kong Hong Kong SAR (P. R. China)
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  • Shuit-Tong Lee

    Corresponding author
    1. Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science City University of Hong Kong Hong Kong SAR (P. R. China)
    • Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science City University of Hong Kong Hong Kong SAR (P. R. China).
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  • This work is supported by the Research Grants Council of Hong Kong SAR (CityU 3/04C and CityU 101807) and the National 973 project of the Major State Research Development Program of China (Grant No 2006CB933000). Dr. Peng thanks the support of National Natural Science Foundation of China (Grant No 50702010), Beijing Natural Science Foundation (Grant No 2082013) and National Excellent Doctoral Dissertations of China (Grant No 200743). Supporting Information is available online at Wiley InterScience or from the author.

Abstract

The autonomous motion behavior of metal particles in Si, and the consequential anisotropic etching of silicon and production of Si nanostructures, in particular, Si nanowire arrays in oxidizing hydrofluoric acid solution, has been systematically investigated. It is found that the autonomous motion of metal particles (Ag and Au) in Si is highly uniform, yet directional and preferential along the [100] crystallographic orientation of Si, rather than always being normal to the silicon surface. An electrokinetic model has been formulated, which, for the first time, satisfactorily explains the microscopic dynamic origin of motility of metal particles in Si. According to this model, the power generated in the bipolar electrochemical reaction at a metal particle's surface can be directly converted into mechanical work to propel the tunneling motion of metal particles in Si. The mechanism of pore and wire formation and their dependence on the crystal orientation are discussed. These models not only provide fundamental interpretation of metal-induced formation of pits, porous silicon, and silicon nanowires and nanopores, they also reveal that metal particles in the metal/Si system could work as a self-propelled nanomotor. Significantly, it provides a facile approach to produce various Si nanostructures, especially ordered Si nanowire arrays from Si wafers of desired properties.

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