Band filling control in ET salts

In order to carry out the band filling control in organic conductors, numerous ET [=bis(ethylenedithio)tetrathiafulvalene] salts including dianions were prepared. Among them, the donor arrangement of β42×2-ET4(MCl42−) 1,1,2-trichloroethane (TCE) [M=Co, Zn] is similar to that of λ(β42)-ET2(GaCl4−). In those preparation condition, four kinds of doped single crystals were obtained: (a) λ-ET2(GaCl4−)1−x(MCl42−)x; (b) δ′-ET2(GaCl4−)1−x(MCl42−)x; (c) α-ET3(MCl42−)1−x(GaCl4−)x(TCE), and (d) β′-ET3(MCl42−)2−x(GaCl4−)x [M=Co, Zn]. With an increase of x, the electrical resistivity decrease by 1/30 for (a) x=0.06 and (b) x=0.14. The resistivity follows the Arrhenius fitting [∝exp(−Ea/kBT)], where Ea decreases with an increase of x.