Reduction of $\mathrm{C}{\mathrm{u}}_2\mathrm{O}$ Islands Grown on a Cu(100) Surface through Vacuum Annealing

The reduction of $\mathrm{C}{\mathrm{u}}_2\mathrm{O}$ islands grown on Cu(100) surfaces through vacuum annealing was visualized by an in situ ultrahigh vacuum transmission electron microscope. The shrinkage of the island followed a linear decay behavior. The complete reduction of the oxide islands leads to the formation of nanoindentations on the Cu surfaces. A simple phenomenological kinetic model based on the dissociation along the island perimeter suitably describes the reduction behavior of the surface oxide islands.

Figure 1

Comparison of the previously proposed oxide reduction models—“nucleation and growth” model (a), “interface” model (b)—to our proposed “perimeter” model (c) in the reduction of surface oxide islands. The island perimeter is defined in (d).

Figure 2

(a) The initial stages of the island reduction; (b) AFM image of partially reduced oxide islands.

Figure 3

(a) The in situ observation of the reduction of two oxide islands at $750°\mathrm{C}$; (b) the dependence of the area of the two islands on the reduction time, the solid lines correspond to the theoretical fit to the “perimeter model.”

Figure 4

(a) Bright-field TEM image of the Cu(100) film after the complete reduction of the oxide islands, the area with bright contrast is the thinned regions due to the oxide reduction, the inset is an intermediate shape of an island during the reduction; (b) an AFM image showing the surface topology of the Cu film after the oxide reduction, which reveals the nanoindentation array formed on the surface, where the typical depth of the indentation is $\sim 15\mathrm{n}\mathrm{m}$.