Diagnostics of negative ions using probe and laser in plasmas (oxygen discharge)

The present paper deals with diagnostics of negative ions in oxygen in a DC (hollow cathode) discharge and RF (parallel-plate capacitive) discharge wh ere negative ions are rich and play important roles. For the negative ion d iagnostics, the probe technique and the laser photodetachment technique are applied to measure the negative ion density, the density ratio of negative to positive ions, the negative ion temperature as well as the negative ion species. Experimental results obtained by using the above techniques are s hown and discussed. The solution of a rate equation using atomic and molecu lar processes is compared with the experimental results. This helps to sear ch an optimum condition for the production of negative ions for an ion sour ce and plasma processing, etc. (C) 2000 Elsevier Science Ltd. All rights re served.