Bilayer growth of nanoscale Co islands on Cu(111)

Combining kinetic Monte Carlo and molecular static simulations, we follow at the atomic scale the growth of Co nanoislands on Cu(111) surface over a wide range of surface temperatures $(130–300\mathrm{K})$. Atomistic processes responsible for the interlayer mass transport of Co atoms and the formation of 2 ML high nanoislands at temperatures $>200\mathrm{K}$ are revealed. Transition from the two- to the three-dimensional growth mode with decreasing the temperature is demonstrated. Strain relaxations induced in the Cu substrate and in the Co nanoislands are found to have a strong impact on the formation of triangle Co islands at room temperatures. Results of our theoretical studies are supported by the scanning tunneling microscope measurements.

Figure 1

(Color online) Anisotropic corner diffusion is the origin of the growth of triangular Co islands with $A$ step edges. The barriers for operative (suppressed) atomic transitions are demonstrated using white (red/gray) rectangles. Black balls represent Cu atoms; dark gray balls correspond to Co atoms.

Figure 2

(Color online) Interlayer mass transport between the first and the second Co layer is operative at $B$ step. The barriers for operative (suppressed) atomic transitions are demonstrated using white (red/gray) rectangles. The ascended Co atom most likely exhibits the diffusion on top of the 1 ML Co island. Black balls represent Cu atoms; dark and light gray balls correspond to Co atoms.

Figure 3

(Color online) Interlayer mass transport between the second and the third layer of Co islands. The barriers for operative (suppressed) atomic transitions are demonstrated using white (red/gray) rectangles. Black balls represent Cu atoms; dark gray balls correspond to Co atoms of the first layer of Co cluster, light gray to of the second one, and white to of the third one.

Figure 4

(a) The morphology of Cu(111) surface exposed by 0.4 ML of Co atoms at $290\mathrm{K}$: the kMC simulation. (b) The atomic resolution of the area marked on (a) with the white square. (c) The experimentally observed morphology. The area $100\times 100{\mathrm{nm}}^2$ is demonstrated in (a) and (c).

Figure 5

(a) The morphology of Cu(111) surface exposed by 0.4 ML of Co atoms at $250\mathrm{K}$: the kMC simulation. (b) The atomic resolution of the area marked on (a) with the white square. (c) The experimentally observed morphology. The area $100\times 100{\mathrm{nm}}^2$ is demonstrated in (a) and (c).

Figure 6

(a) The morphology of Cu(111) surface exposed by 0.8 ML of Co atoms at $135\mathrm{K}$: the kMC simulation. (b) The atomic resolution of the area marked on (a) with the white square. (c) The experimentally observed morphology. The area $100\times 100{\mathrm{nm}}^2$ is demonstrated in (a) and (c).

Figure 7

The morphology of Cu(111) surface exposed by 0.4 ML of Co atoms at $290\mathrm{K}$: the kMC simulation. Strain relaxations are excluded. The area $100\times 100{\mathrm{nm}}^2$ is demonstrated.