Dielectric Breakdown in Solids

It is shown that already at fairly low electronic densities (of the order 10 14 cm -3 ) an electron exchanges energy with other electrons quicker than with lattice vibrations, mainly because collisions with the latter are nearly elastic. The notation of an electronic temperature T , which in an external field is higher than the lattice temperature, is then introduced and it is shown that a stationary state becomes impossible if the field is above a critical strength F c the breakdown strength. For nonpolar and for polar substances F c can be expressed in terms of the electronic mobility in weak fields, and of other measurable quantities.