Figure 1

(a) Room-temperature STM image ($V_{\mathrm{sample}}=58\mathrm{mV}$, $I_t=35\mathrm{nA}$; 10 nm wide) of the surface oxide. Calculated positions of the ${\mathrm{O}}_s$ atoms are superimposed in the right part of the image. (b) Calculated STM image for voltages near the Fermi level [22]. Threefold and sixfold rotation axes of the oxide are marked by triangles and hexagons, respectively.Reuse & Permissions

Figure 2

The structure obtained by DFT optimization: (a) the side view, (b) the interface, and (c) the surface. The yellow grids in (b) and (c) indicate the distorted hexagonal ${\mathrm{Al}}_s$ lattice, and yellow symbols mark the rotation axes of the unit cell, which is sketched in (d).Reuse & Permissions

Figure 3

Experimental (a), (b) and calculated (c), (d) STM images near the conduction band edge [18]. The unit cell and the threefold rotation axes are indicated. Arrows mark extra defects [21]. (e),(f) Images obtained at $+3.1\mathrm{V}$ after deposition of 0.7 and 3 Pd atoms per unit cell, respectively. The line scans (g) through the unit cell corner are most easily explained by 1, 2, and 3 Pd atoms in the corner hole. (h) Side view of the calculated model with 3 Pd atoms in the corner hole. (i) Mosaic of calculated STM images ($+2.3\mathrm{V}$) with 0–3 Pd atoms in the corner hole.Reuse & Permissions

Figure 4

(a) AFM image with hexagonal features marked [20]. (b) Structure model showing only the ${\mathrm{O}}_s$ atoms (dots) and ${\mathrm{Al}}_i$ atoms (gray disks). ${\mathrm{Al}}_i$ hexagons with ${\mathrm{O}}_s$ exactly above ${\mathrm{Al}}_i$ are marked.Reuse & Permissions

Figure 5

STM images (80 nm wide) after deposition of 1 Å Fe (a) without and (b) with predeposition of a 0.03 Å Pd seed layer.Reuse & Permissions