Surface conditions and electrical breakdown characteristics of ozonized water treated copper electrodes of a vacuum gap

Ozonized water treatment has the advantages that organic contaminants can be removed to produce a passivated oxidized film on the surface and the treated surface condition can be kept in air. This technique has been applied to the surface treatment of oxygen-free copper electrodes. Experimental results revealed that the breakdown field at the 1st application of voltage was not always improved, but a significant conditioning effect was obtained without any in-situ precautions. Moreover, additional in-situ sputter cleaning on the ozonized water treated surface improved the 1st breakdown field. Surface analysis clarified that after the ozonized water treatment, the electrode surface was covered with an oxidized film (CuO) and this film was removed to expose bulk copper after conditioning by 500 repetitive breakdowns caused by applying impulse voltages. These results can be attributed to the characteristic that the treated surface can be kept in air.