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We investigate the memory properties of the ITO/graphene oxide/Al diodes. It is found that the devices show different memory behaviors with the diverse geometry and thickness of Al. When the thickness of the Al electrode is relatively thick, the device of the cross-point Al electrode shows a three-level memory effect, and the counterpart device of the cross-bar Al electrode exhibits a volatile static random access memory effect. When the thickness of the Al electrode is thinner, the above devices demonstrate a flash memory effect. The different memory behaviors of ITO/GO/Al diodes are ascribed to the mode and degree of reduction and oxidation of GO.

Al/ZnO/P++-Si diodes exhibit typical unipolar resistive switching behaviors. The electroforming-free characteristics are observed after annealing the ZnO thin film at 400°C in air. The ON/OFF ratios of the resistance are in the range of 104–105 at a very low operation voltage of 0.1 V, and the devices show good endurance characteristics of over 400 cycles with negligible reduction. Finally, the memory mechanisms of the diodes are proposed on the basis of the current-voltage and resistance-voltage results. These results indicate that Al/ZnO/P++-Si devices have potential applications in nonvolatile memory devices.