Charges in Copper Electrode Surface Conditions Caused by Breakdowns in Ultra-high Vacuum

Influence of Cu electrode surface conditions, such as chemical composition and crystal structure of surface, on electrical breakdown in vacuum has been investigated. The chemical compositions were analyzed by a X-ray photoelectron spectroscopy (XPS) and the crystal structure was quantified by measuring residual stresses. The XPS analysis revealed that electrode surfaces were completely cleaned by repetitive breakdowns. The values of the residual stress varied significantly after 500 breakdowns. From breakdown current voltage waveforms, it was demonstrated that breakdown mechanism might be altered by repetitive breakdowns. The mechanism of breakdowns has been discussed on the basis of field electron emission caused by not only metallic but non metallic mechanism.