Metal nanocrystals grown by vacuum deposition on aligned carbon nanotubes

when the vacuum evaporation method was used to deposit metals, such as Au, Ag, or Cu, on a substrate covered with aligned carbon nanotubes which were fabricated by the microwave-plasma-enhanced chemical vapor deposition metho d, we found that nanoscale single crystals of the metals with well-defined facets were grown on the surfaces of the carbon nanotubes. Nanocrystals ran ging from approximately 50 to 500 nm in diameter were obtained when the dep osition time ranged from 1 to 60 min. Whiskerlike crystals with high aspect ratios could also be found frequently in these nanocrystals, which can be applied in field-emission display devices.