An experimental determination of the fractal dimension at the metal—insulator transition in germanium ‘doped’ by radiation defects

Abstract

This work deals with the determination of the magnitude of the fractal dimension, from the analysis of the temperature dependence of the dc conductivity in the temperature range 1.5–300 K in germanium, disordered by large fluences of fast reactor neutrons, with the radiation defect concentration making it an insulator near the metal–insulator transition. From the reduced activation energy method and the percolation theory of hopping conductivity, the dielectric constants of the samples are calculated. The localization radius is determined. The obtained fractal dimensions are found to satisfy the scaling theory. The value determined for the exponent t is 1.7.