Research ArticleENGINEERING

Nanotwinned metal MEMS films with unprecedented strength and stability

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Science Advances  28 Jun 2017:
Vol. 3, no. 6, e1700685
DOI: 10.1126/sciadv.1700685
  • Fig. 1 Plane-view TEM images of the as-deposited film.

    (A) Bright-field plane-view TEM image. (B) TEM-based orientation map collected using precession-assisted crystal orientation mapping.

  • Fig. 2 Cross-sectional microstructure of the as-deposited film.

    (A) Cross-sectional channeling contrast image showing the columnar microstructure of the deposited film. (B) Bright-field cross-sectional TEM micrograph. (C) Corresponding selected-area electron diffraction pattern indexed for matrix and twin orientations. (D) High-resolution TEM (HRTEM) image taken along the [011] zone axis and revealing high-density planar defects. (E) HRTEM image showing stacking faults and nanotwin lamellae on {111} planes. (F) Magnified view focusing on a few planar defects with better clarity (red, matrix; yellow, stacking fault; blue, twin).

  • Fig. 3 Tensile stress-strain curves of three Ni-Mo-W thin films from the current study compared with previously reported nanocrystalline Ni (11), nanocrystalline Ni-W alloy (12), nanotwinned Cu (13), and polysilicon thin films (14).

    The linear elastic response and ultrahigh strength are highly desirable for MEMS applications.

  • Fig. 4 Excellent thermal and mechanical stability of the Ni83.6Mo14W2.4 films.

    (A) Cumulative area fraction of the in-plane grain size of the Ni83.6Mo14W2.4 films annealed at various temperatures. (B) Cross-sectional TEM image of the film annealed for 1 hour at 600°C. FIB channeling contrast (C) and cross-sectional TEM image of a film that was loaded up to 3.1 GPa (D). No obvious changes in the columnar microstructure or twin size/spacing were observed.

  • Table 1 Chemical composition, elastic modulus, tensile strength, hardness, and activation volume of the sputter-deposited Ni-Mo-W film obtained from WDS, microtensile, and nanoindentation tests.
    Composition (at %)Elastic modulus (GPa)Tensile strength (GPa)Hardness (GPa)Activation volume (b3)
    0.05 s−10.2 s−11 s−1
    Ni83.6±0.2Mo14±0.2W2.4±0.1221 ± 52.8 ± 0.38.95 ± 0.829.1 ± 0.919.24 ± 0.8619.6

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/6/e1700685/DC1

    Supplementary Materials and Methods

    Supplementary Text

    fig. S1. Scanning electron microscopy–EDS and XRD graph of the Ni-Mo-W film.

    fig. S2. Yield strength predicted from the CLS model.

    References (4257)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials and Methods
    • Supplementary Text
    • fig. S1. Scanning electron microscopy–EDS and XRD graph of the Ni-Mo-W film.
    • fig. S2. Yield strength predicted from the CLS model.
    • References (42–57)

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