Surface modification of zinc oxide nanoparticles influences the electronic memory effects in ZnO-polystyrene diodes

Resistive switching effects in diode structures with a spin-coated active layer containing zinc oxide (ZnO) nanoparticles in a polystyrene matrix are studied. The switching effect can be influenced by modification of the surface of the nanoparticles with coordinating ligands (amines and thiols). Using n-propylamine as a ligand, memory effects are observed without the diodes having undergone the forming step that is usually required before switching effects can be observed in bulk metal oxides. Memory effects are characterized by impedance spectroscopy and temperature-dependent current-voltage measurements and involve a spontaneous, thermally activated gradual transition from a state with high frequency independent conduction to a state with lower conductivity.