The size distribution of metal clusters produced in plasma-discharge hollow-cathode source

The mean size of Cu clusters produced in a hollow-cathode, dc plasma-discha rge source, increases significantly with decreasing flow rate and less pron ouncedly with increasing Ar/He abundance ratio and increasing discharge cur rent. The effect of pressure is mixed. Between 0.4 and 0.6 mbar the size is not affected. Above 0.6 mbar, the size increases significantly with increa sing pressure. With the help of the above parameters, the mean cluster size can be shifted at will between 20 and 250 Angstrom. Implications concernin g the mechanisms associated with clustering in plasma are discussed. (C) 19 99 Acta Metallurgica Inc.