Research ArticleMATERIALS SCIENCE

Unraveling the atomic structure, ripening behavior, and electronic structure of supported Au20 clusters

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Science Advances  03 Jan 2020:
Vol. 6, no. 1, eaay4289
DOI: 10.1126/sciadv.aay4289
  • Fig. 1 Evidence of the pyramidal Au20 clusters on ultrathin NaCl films.

    (A) STM topography image (200 nm by 200 nm) of Au20 clusters on 3L and 4L NaCl islands (V = −2.0 V, I = 0.02 nA). Three Au20 clusters are indicated by the black arrows. The one in the inset (dimensions, 80 nm by 73 nm) is on top of a 3L NaCl film, while the two others are on top of 4L NaCl. (B and C) Triangular-shaped Au20 clusters with one atom on top, imaged with Cl-functionalized STM tips. Dimensions for both (B) and (C), 10 nm by 10 nm. (D and E) Three-dimensional views (with fast Fourier transform filtering) of the clusters in (B) and (C), respectively. (F) Normalized dI/dV [(dI/dV)/(I/V)] spectra taken on a Au20 cluster on 3L NaCl. Eg is the energy gap around the Fermi level.

  • Fig. 2 DFT simulation of the structural and electronic properties of a pyramidal Au20 cluster.

    (A) Side view and (B) top view of the optimized structure of a Au20 cluster on 3L NaCl/Au(111). The theoretical STM measured height (0.94 ± 0.01 nm) for a Au20 cluster on NaCl is the vertical distance between the top atom of Au20 and the NaCl surface, as indicated by the dashed lines in (A). (C) DOS curve of a free Au20 cluster. (D) Projected DOS (PDOS) curve for a Au20 cluster supported on 3L NaCl/Au(111).

  • Fig. 3 Smoluchowski ripening of Au20 clusters on ultrathin NaCl film.

    (A) STM topography image of high-coverage Au20 clusters on 3L NaCl/Au(111) (size, 100 nm by 100 nm; V = 1.5 V, I = 0.05 nA), using a normal STM metal tip. (B) Size distribution of more than 300 Au20n (n = 1, 2, …) clusters on 3L NaCl/Au(111), where the counted number of clusters is plotted as function of their height and width. (C) Histogram of the height (with respect to the surrounding NaCl surface) distribution of clusters on 3L NaCl/Au(111). Note that (B) and (C) share the same horizontal axis.

  • Fig. 4 Electronic properties of Au20, Au40, and Au60.

    (A) STM topography image (size, 46 nm by 32 nm; V = 1.5 V, I = 0.05 nA) of three clusters (Au20, Au40, and Au60) on 3L NaCl/Au(111) with heights of 0.85, 1.1, and 1.3 nm, respectively, using a normal STM metal tip. (B) The corresponding dI/dV spectra of the three clusters in (A), using the same STM tip.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/1/eaay4289/DC1

    Fig. S1. Additional (next to Fig. 1, B and C) STM topography image of a Au20 cluster on 3L NaCl/Au(111), imaged with a Cl-functionalized tip.

    Fig. S2. Series of dI/dV spectra recorded on different Au20 clusters with different conditions of STM tip apex.

    Fig. S3. Electrostatic model to estimate the capacitance of Au20/NaCl/Au(111) system.

    Fig. S4. Electrostatic model to estimate the capacitance of Au40/NaCl/Au(111) and Au60/NaCl/Au(111) systems.

    Fig. S5. High-resolution STM images for supported Au40 and Au60 clusters.

    Table S1. The relationship between distortion and the HL gap for supported Au20.

    Reference (42)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Additional (next to Fig. 1, B and C) STM topography image of a Au20 cluster on 3L NaCl/Au(111), imaged with a Cl-functionalized tip.
    • Fig. S2. Series of dI/dV spectra recorded on different Au20 clusters with different conditions of STM tip apex.
    • Fig. S3. Electrostatic model to estimate the capacitance of Au20/NaCl/Au(111) system.
    • Fig. S4. Electrostatic model to estimate the capacitance of Au40/NaCl/Au(111) and Au60/NaCl/Au(111) systems.
    • Fig. S5. High-resolution STM images for supported Au40 and Au60 clusters.
    • Table S1. The relationship between distortion and the HL gap for supported Au20.
    • Reference (42)

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