Enhanced resistive switching characteristics in Al₂O₃ memory devices by embedded Ag nanoparticles

In this paper, Al₂O₃/Ag/Al₂O₃ sandwiched thin films were deposited by magnetron sputtering. Al₂O₃ thin films with embedded Ag nanoparticles (AgNPs) have been fabricated by adopting appropriate experimental parameters. The measurements on the resistive switching behaviors demonstrated that the embedded AgNPs could substantially enhance the local electric field, and effectively reduce the switching voltages, resulting in a sharply increased OFF/ON ratio up to 10⁶ at 0.5 V. Furthermore, the cycling stability was considerably improved owing to the reduced randomness for the formation and rupture of conductive filaments (CFs). AgNPs could also contribute with movable Ag ions, and the Ti top electrode usually reacts with Al₂O₃ promoting the formation of oxygen vacancies. As a result, a hybrid CF with better high-temperature stability was induced. Comparatively, if the embedded Ag sublayer is smooth, the switching parameters become dispersive owing to the random formation and rupture of CFs, and the switching performance is deteriorated. A physical model was proposed to understand the effect of the embedded AgNPs.