Dielectric breakdown on LiF cleavage surfaces in compressed N2 gas

摘要

This paper presents a study of electrical breakdown effects on LiF cleavage surfaces situated in compressed nitrogen gas. The object of interest is the (100) dendrite. As first reported by Gilman and stauff,1 this dendrite forms extensive surface patterns on the cleavage face of LiF crystals situated in dielectric liquids when subjected to dc positive (dominant pattern) and negative breakdown voltage. Its classification as a dislocation feature was not accepted by workers at NRL2 who found it to be grooved and channeled. However, since dislocation spike structures, known as screw pairs, were found about some dielectric breakdown paths, 3 the question of primacy was not resolved. According to the basic observations and ideas of von Hippel, 4 substantiated by the work of Cooper and Elliott5 and of Davisson, 6 and treated theoretically by Offenbacher and Callen, 7 the dielectric breakdown path is produced by the disruptive action of oriented electron avalanches which results initially in the formation of dislocation-free, plasma-containing, grooves and channels. The orientation is due to the Brillouin zone structure of the normal modes of lattice vibration. Gilman and stauff1 have proposed that dielectric breakdown is preceded by a discontinuous nucleation of dislocation loops.