STM topography and manipulation of single Au atoms on Si(100)

The low-temperature (12 K) adsorption of single Au atoms on Si(100) is studied by scanning tunneling microscopy (STM). Comparison between experimental and calculated STM topographies as well as density-functional-theory calculations of the adsorption energies enable us to identify two adsorption configurations of Au atoms between Si-dimer rows (BDRs) and on top of Si-dimer rows (TDRs). In both adsorption configurations, the Au atoms are covalently bound to two Si atoms through a partial electron transfer from Si to Au. STM manipulation confirms that the TDR adsorption configuration is metastable, whereas the BDR one is the most stable configuration.

Figure 1

$93\times 117{\text{Å}}^2$ STM topography of the silicon surface after adsorption of Au atoms (9 K). Arrows (1) or (3) indicate the position of BDR Au-atoms configurations while arrow (2) indicates the TDR Au atom.

Figure 2

(Color online) (a) and (b) are $19.2\times 19.2{\text{Å}}^2$ STM topographies $\left(I=70\text{pA}\right)$ of an Au atom in the BDR configuration at $V_s=-2\text{V}$ and $V_s=+0.75\text{V}$, respectively. (c) and (d) are the $19.2\times 17{\text{Å}}^2$ calculated STM topographies of (a) and (b). (e) is a ball-and-stick representation of the BDR configuration used for the calculation of (c) and (d).

Figure 3

(Color online) (a) and (b) are $19.2\times 19.2{\text{Å}}^2$ STM topographies $\left(I=70\text{pA}\right)$ of an Au atom in the TDR(2) configuration at $V_s=-2\text{V}$ and $V_s=+2\text{V}$, respectively. (c) and (d) are the $19.2\times 17{\text{Å}}^2$ calculated STM topographies of (a) and (b). (e) is a ball-and-stick representation of the TDR(2) configuration used for the calculation of (c) and (d).

Figure 4

(Color online) [(a)–(c)] Ball-and-stick representations of the BDR, TDR(1), and TDR(2) configurations, respectively.

Figure 5

(Color online) (a) and (b) are charge-density contour of the BDR and TDR(2) configurations, respectively.

Figure 6

(Color online) (a) and (b) are $57.8\times 52.8{\text{Å}}^2$ STM topographies ($V_s=-2\text{V}$ and $I=70\text{pA}$) of Au atoms adsorbed on the $\text{Si}\left(100\right)\text{−}2\times 1$ surface before and after a manipulation, respectively. (c) is the recorded current trace during the manipulation applied on the left Au atom in (a) (shown by the dot).