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Destabilization of Ag nanoislands on Ag(100) by adsorbed sulfur
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10.1063/1.3635777
/content/aip/journal/jcp/135/15/10.1063/1.3635777
http://aip.metastore.ingenta.com/content/aip/journal/jcp/135/15/10.1063/1.3635777
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Figures

Image of FIG. 1.
FIG. 1.

STM images showing Ag island coarsening at different θ S at 300 K. Ag coverages are all 0.3 ML, and STM images are 50 nm × 50 nm. Column (a): clean Ag/Ag(100), 86, 145, 210 min after Ag deposition. Column (b): 0.034 ML sulfur on Ag/Ag(100), 78, 120, 154 min after Ag deposition (14, 58, 90 min after sulfur deposition). Column (c): 0.083 ML sulfur on Ag/Ag(100), 90, 155, 215 min after Ag deposition (20, 85, 145 min after sulfur deposition). Column (d): 0.12 ML sulfur on Ag/Ag(100), 78, 124, 168 min after Ag deposition (9, 55, 99 min after sulfur deposition). Column (e): 0.21 ML sulfur on Ag/Ag(100), 99, 150, 204 min after Ag deposition (2, 53, 107 min after sulfur deposition).

Image of FIG. 2.
FIG. 2.

Individual Ag island decay rate at different S coverages on Ag/Ag(100). Each filled square is an average value, and the error bars show the entire range of rates measured for a given θ S. The open square at 0 coverage is an estimate of the rate of OR for a Ag island in the absence of sulfur: 0.0006 nm2/s.

Image of FIG. 3.
FIG. 3.

Island area vs. time at θ S = 0.12 on Ag/Ag(100). The arrow in the STM inset shows the island monitored. The circle shows a small island that disappears at about 3300 s, as indicated by the vertical dashed line. The STM image was recorded 3126 s after sulfur deposition ended and its size is 49.6 nm × 49.6 nm.

Image of FIG. 4.
FIG. 4.

Schematic of the different types of sites, and step edges, on Ag(100).

Image of FIG. 5.
FIG. 5.

Schematic of possible adsorption sites for single sulfur atoms (yellow on-line). For each configuration, the adsorption energy per sulfur atom is given. In (a)–(d), the surface unit cell used in DFT is p(3×3). (a): Sulfur at a 4fh site on a terrace. There is no difference in Ead for a p(2×2) unit cell, within numerical uncertainties. (b): Top sulfur at a 4fh site adjacent to a corner/kink site. (c): In-plane sulfur at a 4fh site adjacent to a corner/kink site. (d): In-plane sulfur at a 4fh site adjacent to two Ag atoms. (e) In-plane sulfur at a pseudo-3fh site along a close-packed step. The surface unit cell in DFT is p(3×2).

Image of FIG. 6.
FIG. 6.

Clusters of four Ag atoms with two S atoms. For each system, the adsorption energy per sulfur atom is given. In-plane sulfur atoms are slightly darker (orange on-line) than on-top sulfur atoms (yellow on-line). In (a), the surface unit cell in DFT is p(4×4); results are similar for a p(3×3). In (b) and (c), the surface unit cell in DFT is p(3×3).

Image of FIG. 7.
FIG. 7.

Models of possible Ag step configurations decorated by sulfur. For each configuration, the adsorption energy per sulfur atom is given. In-plane sulfur atoms are slightly darker (orange on-line) than on-top sulfur atoms (yellow on-line). (a), (b): Models of close-packed steps. (c), (d): Models of steps with kink sites.

Image of FIG. 8.
FIG. 8.

(a) Schematic of an extended, close-packed step edge, with a kink site. S1 and S2 show potential sulfur adsorption sites. (b) Potential energy surface for a Ag atom detaching from a four-atom Ag cluster as illustrated in the schematics. The surface unit cell in DFT is p(4×4). (c) Extrapolation of the potential energy surface to a Ag atom far away from the Ag cluster, using DFT calculations of isolated Ag atoms.35

Image of FIG. 9.
FIG. 9.

Left side: Potential energy surface for a AgS2 cluster detaching from a four-atom Ag cluster, as illustrated in the schematics. The surface unit cell in DFT is p(4×4). In-plane sulfur atoms are slightly darker (orange on-line) than on-top sulfur atoms (yellow on-line). Right side: Extrapolation of the potential energy surface far from the Ag cluster, using DFT calculations of isolated AgS2 clusters, as illustrated in the schematics. The formation energy of AgS2 is calculated relative to sulfur in the p(2×2) overlayer.

Image of FIG. 10.
FIG. 10.

Schematic of the (√17 × √17)R14° structure for sulfur on Ag(100), discussed in detail in Ref. 18. Ovals encase S-Ag-S motifs like those favored at extended step edges, with one top sulfur and one in-plane sulfur. The square shows the √17 surface unit cell. In-plane sulfur atoms are slightly darker (orange on-line) than on-top sulfur atoms (yellow on-line).

Image of FIG. 11.
FIG. 11.

Left side: Potential energy surface for a Ag vacancy detaching from a model kink site, as shown in the schematics. The site marked S1 is a sulfur adsorption site used to test sulfur's effect on the energy barrier going from (e) to (d), for reasons described in the text. The surface unit cell used in DFT is p(4×3). Right side: Extrapolation of the potential energy surface far from the Ag cluster, using DFT calculations of isolated Ag vacancies.35

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/content/aip/journal/jcp/135/15/10.1063/1.3635777
2011-10-17
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Destabilization of Ag nanoislands on Ag(100) by adsorbed sulfur
http://aip.metastore.ingenta.com/content/aip/journal/jcp/135/15/10.1063/1.3635777
10.1063/1.3635777
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