Superionic conductivity and switching effect with memory in TlInSe2 and TlInTe2 crystals

The temperature dependences of the conductivity sigma(T) and the switching and memory effects in one-dimensional TlInSe2 and TlInTe2 single crystals have been studied. A specific feature is found in the dependence sigma(T) above 333 K, which is related to the transition of crystals to the state with superionic conductivity. It is suggested that the ion conductivity is caused by the diffusion of Tl+ ions over vacancies in the thallium sublattice between (In3+Te (2) (2-) )(-) and (In3+Se (2) (2-) )(-) nanochains (nanorods). S-type switching and memory effects are revealed in TlInSe2 and TlInTe2 crystals, as well as voltage oscillations in the range of negative differential resistance. It is suggested that the switching effect and voltage oscillations are related to the transition of crystals to the superionic state, which is accompanied by melting of the Tl sublattice. The effect of electric-field-induced transition of TlInSe2 and TlInTe2 crystals to the superionic state is found.