Non-Ohmic electrical conductivity and giant dielectric constant in the quasi-one-dimensional semiconductor methyltriphenylarsonium ditetracyanoquinodimethanide

Results of measurements of the resistivity ρ and the dielectric constant K of the one-dimensional organic semiconductor methyltriphenylarsonium ditetracyanoquinodimethanide are described. Large single crystals of the highly purified compound were grown and ρ determined as a function of temperature T; K was measured over a range of both T and frequency. The activation energy for both ρ and K is found to be the same, 0.41 eV. The resistivity is non-Ohmic and the dielectric constant is quite large. We develop a model which explains the magnitude and temperature dependence of both the non-Ohmic conductivity and the dielectric constant in terms of charged barriers resulting from imperfections (including impurities) in the crystal. The presence of these barriers is verified semiquantitatively using nuclear and electron-spin resonance.