ABSTRACT
As is known, all substances depending on their electro-conductivity are divided
into three groups: conductors (usually metals) with a resistance of 10-6-10-3 Ohm⋅cm,
dielectrics with a resistance of 109-1020 Ohm⋅cm, and semiconductors (many nativegrown and artificial crystals) covering an enormous intermediate range of values of spe-
cific electrical resistance.
