Epitaxy of copper on α-Al2O3(0 0 1) by atomic layer deposition

A combined X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) study have been carried out on copper films grown by atomic layer deposition at 400 °C. The copper films have been grown on single crystalline (0 0 1) oriented α-Al2O3 up to a thickness of 500 nm. The films were relaxed and the diffraction peak broadening in 2θ was mainly dependent on the copper grain size. Broadening of the diffraction peaks in ω was found to be related to defects (mosaicity and intrinsic microstrain). The deposited films were epitaxial and grew with the (1 1 1) plane in parallel to the substrate surface. Extensive twinning in the copper grains in different Cu〈1 1 1〉 directions occurred according to the TEM study, both in directions perpendicular to the substrate surface ([1 1 1] and [1¯1¯1¯]) and along other 〈1 1 1〉 directions as well. As an effect of a (1¯11) twin, an extra Cu(5 1 1) orientation was present in the XRD data.