Bismuth onion structured nanospheres with the same structure as carbon onions have been synthesized and observed. The nanospheres were synthesized through a hydrothermal method using bismuth hydroxide and silicon wafer as reactants. By controlling the heating temperature, heating time, and the pressure, nanoscale bismuth spheres can be in situ synthesized on silicon wafer, and forms a bismuth onion film on the substrate. The electronic property of the films was investigated. A formation mechanism of the formation of bismuth onions and the onion film has been proposed on the basis of experimental observations. (C) 2010 Elsevier B.V. All rights reserved.