Dc conductivity of tetrathiofulvalene bromide (TTF-Brn) and TTF-In single crystals

Tetrathiofulvalene (TTF) combines with the halogens to form crystals with interesting electrical properties due to the segregated stacking of the TTF molecules. The monoclinic forms of TTF-In and TTF-Brn (n∼0.7) have a high conductivity [100-550 (Ωcm)-1] which is almost temperature independent for a very broad region near room temperature but display a thermally activated conductivity at low temperature. Unlike monoclinic TTF-Brn, monoclinic TTF-In displays a strong hysteresis in its conductivity upon temperature cycling. The conductivity of the orthorhombic form of TTF-In (n=2) is about five orders of magnitude lower than the monoclinic form at room temperature and is thermally activated over the entire temperature range.