The changing of initial state in a strong electric field and memory effect in chalcogenides

Our preliminary investigations have shown that information recording based on glass-crystal phase transition, which is induced by pulse of electric field in the chalcogenide glassy semiconductors, has the following interesting peculiarity. Memory state arises not from semiconductors but from metal type state. This state is due to switching effect in thin films, which have strong non-linear current-voltage characteristics and inside which the phase transition from semiconductor to metal type conductivity takes place. The abovementioned effect very strong influences on a current filament characteristics, i.e. on the area where memory state arises. In the present paper it is shown that thermo-stimulated tunnel ionization of negative-U centers in a strong electric field may be the mechanism, which is responsible for appearance of metal like state.