Annular profile of dust density near RF-powered electrode in a capacitively coupled plasma

Annular formation of externaly injected dust particles was observed near an RF-powered electrode by means of a laser light scattering method. Dust particles near the RF electrode were found to form an annular profile in a radial symmetrical shape with a diameter of about 1 cm, locating at the edge of the electrode. Dust particles were inferred to be negatively charged from the fact that the absolute value of the self-biased voltage at the RF-powered electrode decreases when introducing dust particles into the plasma, The mechanism of annular dust formation was ascribed to the RF sheath potential, based on qualitative investigations of the horizontal and vertical force balance acting on the dust particles. It was also found that the annular dust formation shape was strongly dependent on the RF sheath voltage.