Transient/persistent switching of CU-DCNQI by pressure and light

Summary form only given. Even at ambient pressure most Cu-DCNQI systems exhibit phase transitions at T/sub c/(1bar) from a CN-copper-CN bridged metallic 3-d conductivity /spl sigma/ to a serniconductive I-d behavior. This is accompanied by hysteresis effects, most pronounced by alloyed Cu-salts (deuterated (d/sub 6/) / undeuterated (hs) DCNQI/sup 1/) which exhibit a reentry of a (3-d) at T/sub c/,(reentry). Applying preasure on a contacted crystal in a gas cell placed in our ESR-machine, these phase transitions in /spl sigma/ can be induced at temperatures above T/sub c/(1 bar), accompanied with the onset of a strong Cu/sup 2+/-ESR signal I(ESR) of localized spins. Shifts in T/sub c/ of 10K are easily achieved by p=200bar i.e. at (d/sub 6/)-DCNQI-Cu. Releasing the pressure, the system stays switched off in /spl sigma/ and I(ESR) persists. Short light pulses switch on /spl sigma/ and switch off I(ESR) and vice versa, working just above T/sub c/(reentry) of alloyed (d/sub 6//h/sub 8/)-DCNQI-Cu. Under persistent pressure, light pulses lead to fast transient /spl sigma/ response or to discrete resistivity changes adjustable by p and T. This holds for (h/sub 8/)-DCNQI-Cu under pressure as well, although at ambient pressure no phase transition is detected. These features are discussed in respect to an application for nanostructures and molecular electronics. We want to switch back the volume effect of the pressure only fractionally by using electron beam lithography on selected surface areas.