The effects of a low temperature irradiation on TTF-TCNQ and related compounds

L. Zuppiroli , S. Bouffard

Measurements of the electrical conductivity of TTF-TCNQ, TSF-TCNQ and HMTSF-TCNQ samples which have been irradiated at 21 K with fast neutrons (1 MeV) are presented. At this temperature a fast neutron dose of 4.3 x 1015 neutrons/cm2 increases the longitudinal resistivity of HMTSF-TCNQ by a factor of 5, decreases the longitudinal resistivity of TTF-TCNQ by a factor of 5 and decreases its transverse resistivity by an order of magnitude, and decreases the longitudinal resistivity of TSF-TCNQ by an order of magnitude. A phenomenological quantitative analysis of the resistivity versus dose curves has been made. In this analysis the irradiated TCNQ salts are considered to be inhomogeneous materials composed of small damaged volumes more (or less) conducting than the pure material. These damaged volumes are included at random in a matrix of undamaged crystal. With this effective medium model, one can estimate the number of atoms n included in the transformed volume around a radiation induced point defect. For the materials above we found the following values : (absolute values of n are known within a factor 4 or 5). The annealing effects on the low temperature radiation induced defects have been examined and an annealing peak is observed about 140 K in TTF-TCNQ and 85 K in TSF-TCNQ. These results suggest that, at low temperature, irradiated crystals of TCNQ salts as well as so called pure crystals contain macroscopic inhomogeneities due to defects. All the materials are probably mixtures of more or less distorded volumes.

Mots clés: neutron effects; one dimensional conductivity; organic compounds

Domaines: Articles anciens

L. Zuppiroli, S. Bouffard. The effects of a low temperature irradiation on TTF-TCNQ and related compounds. Journal de Physique, 1980, 41 (3), pp.291-297. ⟨10.1051/jphys:01980004103029100⟩. ⟨jpa-00209245⟩