Resistive switching characteristics of Al2O3/ZnO bilayer thin films for flexible memory applications
Unipolar resistive switching behavior of the ZnO and Al2O3/ZnO films fabricated on flexible substrates by pulse laser deposition were studied in this paper. The films were deposited at room temperature without post-annealing treatment during the process. X-ray diffraction results indicated that ZnO film has a dominant peak at (002). Scanning electron microscopy observation showed a columnar grain structure of the ZnO film to the substrate. The bilayer device of Al2O3/ZnO films had stable resistive switching behaviors with good endurance performance of more than 200 cycles, high resistive switching ratio of over 103 at a read voltage of 0.1V, which was better than that of the single oxide layer device of ZnO film. A possible resistive switching filamentary mode was demonstrated in this paper. The conduction mechanisms of high and low resistance states can be explained by space charge limited conduction and Ohmic’s behavior. The endurance of the BL device was not degraded upon bending cycles, which indicates the potential of the flexible resistive switching random access memory applications.