The effects of additive ions on the generation of metallic nanoparticles were evaluated using a corona induced supersonic nozzle. Applying the corona discharge to the nanoparticle generator, a tungsten needle and the supersonic nozzle are used as an anode electrode and a cathode electrode respectively. The corona ions act as nuclei for the silver vapor condensation. The ion density was controlled precisely as varying the applied voltage between electrode and nozzle.
The nanoparticle generator consists of two chambers; an evaporation chamber and a deposition chamber. Two chambers are separated by the supersonic nozzle of 0.5 mm throat diameter. Our experiments performed at the crucible temperature of 1030 ℃, the evaporation chamber pressure of 2.4torr, and the deposition chamber pressure of 0.016torr. Ar is selected as carrier gas, which flow rate is fixed at 8.9e-5 g/sec. Silver powder of 0.2mm is used as a metal vapor source, and it is supplied to the carrier gas as the mole fraction ratio of 0.04. ion current (0.41, 0.61, 0.72 μ A). Ejected current, which varies from 0.41 to 0.72 μ A as increasing the applied voltage, is measured from the difference between total current and leakage current. To measure the size distribution and the mean diameter of silver particles, TEM(transmission electron microscopy) and SEM(scanning electron microscopy) images were taken.
The mean diameter of the silver particle decreases as the ion density increases. However, the number concentration of the silver particle tended to increase with the ion density. The size distribution is more uniform as the ion density increases.
