TMTSF SEMICONDUCTORS,ORGANIC

Because of the softness of organic metals one expects them to show interesting behavior under applied pressures. This had been demonstrated earlier by Jerome and co-workers on several compounds and in the case of TMTSF-DMTCNQ (DMTCNQ = dimethyltetracyanoqui-nodimethane) a pressure of 10 kbar transforms it abruptly from a Peierls semiconductor with Tm = 50 K to a metal at all temperatures (91). When the temperature-dependent resistance of the (TMTSF)2X family became known, the very low transition temperatures in some of the compounds suggested that these salts would easily become metallic, and maybe even superconducting, under pressure. 

Results are described for three new highly conducting organic solids, all based on substituted TCNQ-derivatives TMTSF-2,5-dimethyl-TCNQ /TMTSF-DMTCNQ/ 1 1 shows "normal" conductivity vs.temperature behaviour, i.e. metallic conductivity at higher temperatures followed by a metal-semiconductor transition as the temperature is decreased below 5o K. 

The organic solid TMTSF-DMTCNQ /6/ /Fig. 1/ has a room-temperature doncudtivity of about 5oo (-Cl cmf1, and the temperature dependence of the conductivity shows "normal" behaviour i.e. the conductivity increases /by a factor of approximately lo/ tc a sharp maximum - in this case at 50 K. Below this temperature the material undergoes the characteristic metal-semiconductor transition. 

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