Transition-pathway models of atomic diffusion on fcc metal surfaces. II. Stepped surfaces

Action-derived molecular dynamics was demonstrated in the companion paper (Paper I) to be effective for the analysis of atomic surface diffusion. The method is here applied to the search of minimum-energy paths and the calculation of activation energy barriers in more complex single-adatom diffusion processes on fcc metal surfaces containing steps. Diverse diffusion routes are investigated along and across one- or two-layer steps on different surface orientations. Fundamental diffusion mechanisms near the step corners are also studied. Results are analyzed in relation to the island growth mechanism, which is of importance to surface nanoengineering.

Figure 1

Diffusion directions on stepped (001) surfaces. [110] step on the (001) surface (top) and [100] step on the (001) surface (bottom).

Figure 2

(Color online) Pathway snapshots of an adatom diffusion across the step. Hopping-type climbing (left) and exchange-type climbing (right).

Figure 3

Diffusion directions on stepped (111) surfaces. $A$-type step on the (111) surface (top) and $B$-type step on the (111) surface (bottom).

Figure 4

Diffusion directions on stepped (110) surfaces. $\left[1\overline{1}0\right]$ step on the (110) surface (top) and [100] step on the (110) surface (bottom).

Figure 5

Diffusion directions on double-stepped (001) surfaces. [110] step on the (001) surface (top) and [001] step on the (001) surface (bottom).

Figure 6

(Color online) Pathway snapshots of climbing on a double-stepped surface. Hopping (top row), single exchange (middle row), and double exchange (bottom row). Each row proceeds from left to right.

Figure 7

Diffusion directions on double-stepped (111) surfaces. $A$-type step on the (111) surface (top) and $B$-type step on the (111) surface (bottom).

Figure 8

Diffusion directions on double-stepped (110) surfaces. $\left[1\overline{1}0\right]$ step on the (110) surface (top) and [001] step on the (110) surface (bottom).

Figure 9

Horizontal diffusion directions to the step corners on the (001) surface. Diffusion to the [110] step corner (top) and diffusion to the [100] step corner (bottom).

Figure 10

Descending diffusion directions to the step corners on the (001) surface. Diffusion to the [110] step corner (top) and diffusion to the [100] step corner (bottom).

Figure 11

Horizontal diffusion directions to the step corners on the (111) surface. Diffusion to the $A$-step corner (top) and diffusion to the $B$-step corner (bottom).

Figure 12

Descending diffusion directions to the step corners on the (111) surface. Diffusion to the $A$-step corner (top) and diffusion to the $B$-step corner (bottom).

Figure 13

Horizontal diffusion directions to the step corners on the (110) surface. Diffusion to the $\left[1\overline{1}0\right]$ step corner (top) and diffusion to the [001] step corner (bottom).

Figure 14

Descending diffusion directions to the step corners on the (110) surface. Diffusion to the $\left[1\overline{1}0\right]$ step corner (top) and diffusion to the [001] step corner (bottom).