Research ArticleMATERIALS SCIENCE

Complex dewetting scenarios of ultrathin silicon films for large-scale nanoarchitectures

See allHide authors and affiliations

Science Advances  10 Nov 2017:
Vol. 3, no. 11, eaao1472
DOI: 10.1126/sciadv.aao1472
  • Fig. 1 Dewetting of Si on SiO2 for simple and complex patterns.

    (A) AFM images of a simple pattern (square having a 4-μm side) annealed for 3 hours. The left panel shows a well-controlled dewetting, whereas the central and right panels show pathologic behaviors where the patch broke in an uncontrolled way. (B) Same as (A) for a 3-μm side squared patch. (C) AFM image of a simple pattern having a 1.7-μm side annealed for 3 hours. (D) Same as (C) for a 600-nm sided simple pattern. Further characterization is provided in fig. S2. (E) SEM images of a simple pattern having a 1.7-μm side annealed for 15 min. The center-right inset displays the full pattern. The areas highlighted with a red and blue rectangle are shown in the top and bottom panels, respectively. The top panel displays the case of a flat dewetting front. The bottom panel shows a kink in the dewetting front. Small tips on the patch edge and on the SiO2 are highlighted by white arrows. (F) Left: AFM image of a 5-μm square patch with three holes on the main diagonal annealed for 3 hours (the original shape of the complex pattern is highlighted in black). Right: Same as the left panel for a SEM image. The following distances are highlighted on the SEM images: D, separation of the two islands formed at the patch corners; d, separation of the corners of the two large connected structures; L, side of the large connected structures; l, size of the island forming at the extremity of the large connected structures. (G) Statistical distribution of l (26 repetitions), L (26 repetitions), d (14 repetitions), and D (14 repetitions) (from the top to the bottom panel, respectively) obtained from SEM images. The corresponding SDs from the average value are reported on each panel. Additional characterization of the islands and size statistical distributions are provided in fig. S4.

  • Fig. 2 Structural and optical characterization of dewetted Si on SiO2.

    (A) 3D view of atomic force microscopy (AFM) images of patches annealed for 3 hours. The corresponding 2D view from the top and the shape of the etched pattern are displayed in the fig. S3. (B) Optical dark-field microscopy images. Each panel displays the full patterned area. The bottom right inset in each panel displays an enlarged view of a single dewetted patch. Panels from the top left to the bottom right display patches with an increasing level of complexity of the etched pattern within the main square. The case displayed in A-I corresponds to the PF simulation shown in Fig. 3B (second panel), panel B-I corresponds to Fig. 3C (third panel), panel A-V corresponds to Fig. 3E (fourth panel), and panel B-I corresponds to Fig. 3D (third panel). A quantitative comparison between the experiments and the simulations is provided in Fig. 4.

  • Fig. 3 PF 3D simulations of solid-state dewetting of Si on SiO2.

    (A) Evolution with time of a squared patch with an aspect ratio of 1:40, corresponding to the experimental setup shown in Fig. 1D. Scale bar, 20 arbitrary units. The color scale represents the local curvature of the surface κ. (B) Evolution with time of a simple squared patch with an aspect ratio R = 1:80, leading to the spontaneous formation of a hole at the center. (C) Evolution with time of a squared patch with an aspect ratio R = 1:80 with an additional central hole (with a diameter equal to the height of the film), as in Fig. 2 (A-II). (D) Evolution with time of a squared patch with an aspect ratio R = 1:80 with four holes at the corners, as in Fig. 2 (B-I). (E) Evolution with time of a squared patch with an aspect ratio R = 1:80 with three holes on the diagonal, as in Fig. 2 (A-V). Representative steps of the evolution are selected for each simulation. Complete evolutions, including intermediate stages, can be found in movies S1 to S7. The initial conditions for all the simulations reported here are also shown in the fig. S6.

  • Fig. 4 Time evolution and comparison of dewetting of Si on SiO2 with PF simulations.

    For each panel, two SEM images for ST and LT evolution are reported on the left. Scale bars, 1 μm. Superposition of the top-view outline from the experiments (solid black lines) and rescaled PF simulations (dashed colored lines) are shown in the center. The colors of the simulated morphologies correspond to different R values: blue, 1:40; red, 1:80; green, 1:160. On the right panels, the XOR area of top-view outlines from the experiments and simulations is shown. The percentages corresponding to the relative XOR area with respect to the total area of the corresponding square image are reported on each subfigure. (A) UT-SOI patch, as in Fig. 1C. (B) Patch with a hole in the center. Sizes of the patches for the ST and LT cases are 1.7 and 5 μm, respectively. (C) Patch with three holes along the diagonal, as in Fig. 1F. (D) Patch with a cross in the center, as in Fig. 2 (B-IV). In this panel, the comparisons to two different simulations are shown: top row, R = 1:80; bottom row, R = 1:160. The complete evolutions, as obtained by PF simulations, can be found in movies S1 to S7.

  • Fig. 5 Nanotransfer molding of titania and silica xerogels on silicon and silica substrates.

    (A) Optical dark-field microscopy image of TiO2 motif nanoimprinted on a 44-nm-thick xerogel on silicon, reproducing the original silicon master shown in Fig. 2 (C-V). (B) Optical dark-field microscopy image of a TiO2 motif nanoimprinted on 84-nm-thick film, which is a replica of pattern A-II in Fig. 2. (C) Optical dark-field microscopy image of TiO2 motif nanoimprinted on a 62-nm-thick xerogel, replica of the pattern in panel A-V of Fig. 2 printed on a silica substrate. (D) Dark-field image of an SiO2 motif nanoimprinted on a 110-nm-thick xerogel, replica of the pattern A-IV of Fig. 2. On each figure, the material of the nanoimprinted motif, the substrate in use, the initial thickness of the xerogel t0, and the refractive index of the material after evaporation of the volatile parts are reported. (E) AFM image of one individual nanoimprinted TiO2-based pattern on Si from (B). Scale bar, 1 μm. (F) Height profiles “CENTER” (top) and “SIDE” (bottom) extracted from the AFM image in (E) (red lines) and from the corresponding Si master (black lines) shown in Fig. 3 (A-II). (G) AFM image of one individual SiO2-based pattern nanoimprinted on Si from (D). Scale bar, 1 μm. (H) Height profiles “CENTER” (top) and “SIDE” (bottom) extracted from the AFM image in (G) (red lines) and from the corresponding Si master (black lines) shown in Fig. 2 (A-II).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/11/eaao1472/DC1

    Fabrication and characterization

    Simulations

    Nanoimprinting

    fig. S1. Experimental methods.

    fig. S2. Optical and microscopic characterization of simple structures.

    fig. S3. Characterization of dewetted structures.

    fig. S4. Characterization of the disorder.

    fig. S5. PF modeling.

    fig. S6. Initial states for dewetting.

    fig. S7. Soft nanoimprint lithography process.

    fig. S8. Nanoimprinted SiO2 patterns on a Si substrate.

    movie S1. Simple squared patches with R = 1:40.

    movie S2. Simple squared patches with AR 1:80.

    movie S3. Simple squared patches with R = 1:80 and a central hole.

    movie S4. R = 1:80 and four holes.

    movie S5. R = 1:80 and three holes on the diagonal.

    movie S6. R = 1:80 with cross.

    movie S7. R = 1:160 with cross.

    References (74, 75)

  • Supplementary Materials

    This PDF file includes:

    • Fabrication and characterization
    • Simulations
    • Nanoimprinting
    • fig. S1. Experimental methods.
    • fig. S2. Optical and microscopic characterization of simple structure.
    • fig. S3. Characterization of dewetted structures.
    • fig. S4. Characterization of the disorder.
    • fig. S5. PF modeling.
    • fig. S6. Initial states for dewetting.
    • fig. S7. Soft nanoimprint lithography process.
    • fig. S8. Nanoimprinted SiO2 patterns on a Si substrate.
    • References (74, 75)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.mpg format). Simple squared patches with R = 1:40.
    • movie S2 (.mpg format). Simple squared patches with AR 1:80.
    • movie S3 (.mpg format). Simple squared patches with R = 1:80 and a central hole.
    • movie S4 (.mpg format). R = 1:80 and four holes.
    • movie S5 (.mpg format). R = 1:80 and three holes on the diagonal.
    • movie S6 (.mpg format). R = 1:80 with cross.
    • movie S7 (.mpg format). R = 1:160 with cross.

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article