Epitaxial growth of copper nanowire arrays grown on H-terminated Si(110) using glancing-angle deposition

We report the growth of epitaxial nanowire arrays using the technique of glancing- angle deposition with substrate rotation. Epitaxial copper nanowire arrays were deposited on H-terminated Si(110) using electron beam evaporation. The nanowire arrays were characterized by x-ray diffraction, atomic force microscopy, and scanning electron microscopy. Individual nanowires were confirmed to be single crystalline by examination with transmission electron microscopy. The epitaxial growth involves twin formation with the epitaxial orientation relationships: Cu(111)//Si(110) with Cu[110]//Si[001] and Cu[110//Si[001] for each of the twins. As the angle of incidence is increased, Cu grows as isolated columns with a spacing that increases as the angle of incidence is increased. However, the thickness limit for epitaxial growth is reduced as the angle of incidence is increased, and it is reduced to approximately 300 nm for a deposition angle of 75°. The x-ray rocking curves for samples deposited at increasing polar angles show steadily improving crystal orientation up to a deposition angle of about 35°. Beyond 65° deposition angle, the rocking curves show significantly sharper split diffraction peaks indicating that there are distinct orientations. In addition, the split peaks have a much lower full width at half maximum. The observed behavior is explained based on arguments involving unidirectional diffusion arising from adatom parallel momentum.