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-discharge source, increases significantly with decreasing flow rate and less pronouncedly with increasing Ar/He abundance ratio and increasing discharge current. 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 increasing pressure. With the help of the above parameters, the mean cluster size can be shifted at will between 20 and 250 A. Implications concerning the mechanisms associated with clustering in plasma are discussed.