Self-organization of helium precipitates into elongated channels within metal nanolayers

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Science Advances  10 Nov 2017:
Vol. 3, no. 11, eaao2710
DOI: 10.1126/sciadv.aao2710
  • Fig. 1 Cross-sectional images of He-implanted V/Cu/V samples.

    (A) Dark-field STEM. (B) Bright-field TEM. The Cu layer appears bright in (A) but has low contrast with the neighboring V layers in (B). He precipitates appear dark in (A) and bright in (B). The Pt layer shown in both images is used only for TEM sample preparation and is not present during He implantation.

  • Fig. 2 Plan-view images of He channels.

    Underfocused plan-view TEM micrographs (400-nm underfocus) of the V/Cu/V trilayer after He implantation to fluences of (A) 1015 ions/cm2, (B) 3 × 1015 ions/cm2, (C) 5 × 1015 ions/cm2, and (D) 1016 ions/cm2. An isolated precipitate from a sample implanted to 3 × 1015 ions/cm2 appears (E) bright in underfocus and (F) dark in overfocus imaging conditions (400-nm overfocus), confirming that it is an elongated, He-filled cavity.

  • Fig. 3 Channel growth as a function of implanted He.

    Area coverage of plan-view images with He channels increases as a function of fluence (bottom axis) and He concentration in the Cu layer [top axis, computed using the SRIM code (23)].

  • Fig. 4 Channel connectivity as a function of implanted He.

    The number of kinks (top left inset) and junctions (bottom right inset) per unit He channel length as a function of fluence (bottom axis) and He concentration in the Cu layer (top axis).

  • Fig. 5 Phase-field simulations of He precipitate growth and coalescence.

    (A) Simulation domain with top and bottom boundaries representing Cu/V interfaces, each of which contains one wettable strip (red). (B) Initial distribution of He precipitate nuclei on wettable strips. (C) Growth and coalescence of He precipitates along individual strips. (D) Growth and coalescence of He precipitates wetting opposing interfaces.

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Cross-sectional TEM image of as-prepared V/Cu/V sample.
    • fig. S2. Plan view TEM images of as-prepared V/Cu/V sample.

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