Spontaneous growth of bismuth nanowires on a sputter-deposited thin bismuth film

Thin films of bismuth of thickness 100nm have been deposited onto Si(111) substrates held at 120°C using magnetron sputter deposition. The three-inch magnetrons were operated at DC powers between 30W and 50W to give deposition rates between 0.03 and 0.09nms^-1. Examination of the surface of the thin films using scanning electron microscopy revealed nanowires of diameter 80-120nm and length between 3 and 16μm emerging from the film. An investigation of the effect of deposition rate found little influence on the nanowire diameter, but indicated that some longer nanowires could be found on the film deposited at the lowest rate. A 20nm film grown on glass at 110°C shows a nanowire with dimension of around 50nm. Using a relatively higher rate for the first 25nm followed by a lower rate to 100nm produced some very straight and regular nanorods.