Band filling control in ET salts

Abstract 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 β 42×2 -ET 4 (MCl 4 2− ) 1,1,2-trichloroethane (TCE) [M=Co, Zn] is similar to that of λ(β 42 )-ET 2 (GaCl 4 − ). In those preparation condition, four kinds of doped single crystals were obtained: (a) λ-ET 2 (GaCl 4 − ) 1− x (MCl 4 2− ) x ; (b) δ′-ET 2 (GaCl 4 − ) 1− x (MCl 4 2− ) x ; (c) α-ET 3 (MCl 4 2− ) 1− x (GaCl 4 − ) x (TCE), and (d) β′-ET 3 (MCl 4 2− ) 2− x (GaCl 4 − ) 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(− E a / k B T )], where E a decreases with an increase of x .