Nanoparticle synthesis by ionizing source gas in chemical vapor deposition

A new chemical vapor deposition (CVD) method called ionization CVD, in which reactant gases are ionized, was developed for the synthesis of nanoparticles. In such a CVD method, the particles formed are charged and the repulsive Coulombic force between them suppresses their coagulation, producing non-agglomerated particles that have a relatively high number concentration and small size. A tetraethylorthosilicate (TEOS)/O-2 mixture was ionized by using a sonic-jet corona discharger. All particles formed by the ionization CVD had a negative charge and their sizes and number concentrations were 1/6-1/15 times smaller and 10-150 times higher, respectively, than those of particles formed by conventional CVD. The mean diameter of the smallest particles prepared with ionization was 8.9 nm.