Properties of Vacuum-Insulated Single-Crystal Tungsten Electrodes in High Electric Fields. Part I. Surface Structural Changes

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Abstract
The surface structures of variously oriented single‐crystal tungsten electrodes in a vacuum of ∼2×10−5 Torr have been examined after the application of electric fields leading to breakdown. Electron microscope replica techniques were chiefly used. Various surface irregularities were found, including ``splash'' and ``burn'' areas where material was transferred from one electrode to the other, protrusions and depressions, and identical twin or triplet defects of undetermined origin. However, the most interesting defects were characterized as thermal‐electrical traces, and they clearly resulted from evaporation of atoms from slip steps. It is tentatively suggested that breakdown may be initiated by that electrode most likely to undergo plastic deformation, and that crystal orientation is important in this connection.