Rapid Fabrication of Nanocrystals through in situ Electron Beam Irradiation in a Transmission Electron Microscope

In situ electron-beam irradiation was performed in a transmission electron microscope to fabricate nanocrystals of IV-VI semiconducting lead chalcogenides PbE (E = S, Se, and Te) and low-melting-point metals (Zn, Ga, Sn, and Cd). The source powders consisting particles of 300-1000 nm in diameter were supported on a thin carbon (C) film. A convergent electron beam was focused on an individual particle, which caused partial melting and evaporation of the particle and subsequent nucleation and growth of new nanoparticles on the C film. These nanocrystals are structurally uniform and free of any linear and planar defect and do not have any other impurity contamination. The method is easy to set up and is low in cost and is very fast (several seconds to several minutes) in process. It is believed that this new method can also be employed to synthesize many other material nanocrystals and one-dimensional nanostructures, beyond semiconductors and (low melting point) metals, such as oxides and even sulfides and nitrides.