PRODUCTION OF DIATOMIC AND TRIATOMIC MOLECULAR NEGATIVE-IONS OF GOLD AND COPPER BY SPUTTERING

Monoatomic, diatomic and triatomic negative ions of Au and Cu produced on a surface of the sputtering target of a self-extraction negative ion source were measured. The bias potential applied to the target was varied from 100 to 500 V with respect to a Cs-introduced Ar plasma. The ratios of the polyatomic negative ions to the monoatomic negative ions increased in accordance with the increasing energy of the incident ions, and decreased as the amount of Cs in the discharge was increased. The atomic negative ion fraction can be maintained at a value higher than 90% by controlling these parameters.