A low-energy high-intensity broad-beam ion source was used to study the effects of the ion energy upon the deposition of epitaxial Cu films under ultra-high vacuum conditions. Atomically flat Ge(001) and Si(001) substrates were used for the deposition of 300nm Cu films, using ion energies of between 20 and 100eV. The films were characterized by using X-ray diffraction rocking curve, pole figure and scanning tunnelling microscopic techniques. It was found that primary ion deposition led to improvements in both the surface morphology and the mosaic spread of the films. For energies of more than 37eV, the surface roughness decreased by a factor of almost 2; compared to evaporated Cu films. At an energy of 35eV, the mosaic spread of Cu films which were grown onto Si substrates was only about 2. This was nearly a factor of 2 smaller than that for evaporated Cu. During deposition, at an energy of 25eV, onto Ge substrates the film coherently relaxed the 10% misfit strain via the formation of a tilt boundary which was 4-fold symmetrical towards <111>.

B.W.Karr, Y.W.Kim, I.Petrov, D.B.Bergstrom, D.G.Cahill, J.E.Greene, L.D.Madsen, J.E.Sundgren: Journal of Applied Physics, 1996, 80[12], 6699-705