INITIAL GROWTH-MORPHOLOGY IN MOLECULAR-BEAM EPITAXY OF FCC IRON ON CU(100)

Specular helium atom scattering has been used to study the early stages of growth in epitaxial iron films on a copper (100) substrate. Results are reported for films, up to five monolayers thick, grown at 298 K. The data show that, in the case of helium scattering, the specular intensity can give a picture of the vertical growth morphology even in situations when it is not possible to separate the sharp, coherently scattered contribution to the specular peak from the broad, incoherently scattered contribution to the peak. We conclude that film growth begins with the formation of three-dimensional islands having a small mean size. As the film thickens, there is a trend towards layer-by-layer growth and an increased island size. The results enable us to rule out earlier suggestions that the growth begins in a layer-by-layer fashion with a single or bi-layer structure.