Grain-boundary segregation in nanocrystalline Cu-Bi layers studied with the tomographic atom probe

In an effort to prepare nanocrystalline Bi-doped Cu layers, the Ar sputter deposition technique was applied. In previous works, polycrystalline grain growth on planar substrates was reported. On the apex of W tips with a radius of curvature of about 20-35 nm, we find columnar nanocrystalline grain growth. The Cu bilayers so prepared were characterized by means of the atom probe tomography (APT) and field ion microscopy (FIM). Lamellar structures of grain boundaries and isolated grain boundaries are observed. Without any post-annealing after deposition, we find elevated concentrations of Bi at discrete grain boundaries and in the grains. Copyright (C) 2007 John Wiley & Sons, Ltd.