Photoemission electron microscopy is used to study the thermal decay of Ag islands grown epitaxially on Si(001) surfaces. (2 x 3) Ag reconstructed zones, due to migrating Ag atoms supplied to the surface by the decaying islands, surround each of the islands. The shape of these reconstructed zones depends on the degree of diffusion isotropy in the system. We demonstrate that the imaging of these reconstructed "isocoverage zones" constitutes a unique experimental method for directly observing diffusion fields in epitaxial systems. We describe the dynamics of the thermal decay of the islands and the isozones in the context of a continuum diffusion model.

We have used low energy electron microscopy (LEEM) and photo emission electron microscopy (PEEM) to study the high temperature (620 °C) self-assembly of Ag nanowires on vicinal Si(001), miscut 4° in the [110] direction. After formation of an initial wetting layer, growth of wire-like structures proceeds with subsequent deposition. Simultaneously, compact islands form and the nanowires comprise only a minority of the total Ag deposit. The wires display quasi-one-dimensional behaviour as their length is observed to increase while their width remains constant. The lengths of the wires can be controlled and we have routinely grown wires longer than 100 µm. A kinetically limiting process, wherein mass transport is suppressed in the direction normal to the direction of elongation, is identified as a contributor to the growth of the nanowires.

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