Fabrication and characterization of ZnO thin film memristor using ultra dilute electrodeposition method

Abstract

Memristor has become one of the alternatives to replace the current memory technologies. Instead of titanium dioxide (TiO2), many researches have been done to explore the compatibility of others transition metal oxide (TMO) by using various deposition methods. Recently, the compatibility of zinc oxide (ZnO) to be used as the active layer of memristor has been widely explored. Meanwhile, the usage of organic materials in electronic device has shown a rapid growth as the size demand of devices is increasingly smaller and faster. Future electronics industry depends on the development of organic base semiconductor devices due to their advantages. In this study, the metal-insulator-metal (MIM) of Au/ZnO-Cu2O-CuO/Cu and Au/ZnO/ITO/PET memristor were fabricated using dilute electrodeposition of zinc (Zn) and subsequent thermal oxidation methods at 773 K and 423 K respectively. The 15 s deposition gives the thinnest thin film, 80.67 nm for ZnO-Cu2O-CuO on Cu and 68.10 nm for ZnO on ITO coated PET. The deposited thin film was characterized via X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). On Cu substrate, the XRD result indicates that Zn was oxidized to ZnO and has a wurzite structure. Meanwhile, Cu substrate also was oxidized to Cu2O and CuO. There was formation of needle like structure observed through FESEM after thermal oxidation method. While on ITO coated PET substrate, Zn was oxidized to wurzite ZnO as shown in XRD result with nodule structure of ZnO after the thermal oxidation method. Both Au/ZnO-Cu2O-CuO/Cu and Au/ZnO/ITO/PET sandwich memristive behavior were identified by the pinched hysteresis loop obtained from the I-V measurement. The high resistance state, HRS over low resistance state, LRS ratio of 1.110 and 1.067 respectively were obtained. Empirical study on thermodynamics of ZnO, Cu2O, CuO and diffusivity of Zn2+ and O2- in ZnO shows that zinc vacancy was formed in ZnO layer, thus giving rise to its memristive behavior. The synthesized Au/ZnO-Cu2O-CuO/Cu and Au/ZnO/ITO/PET memristor show potential application in the production of a non-complex and low cost memristor. A flexible Au/ZnO/ITO coated PET memristor produces a comparable result to the Au/ZnO-Cu2O-CuO/Cu memristor and other previous studies on memristor. The flexible memristor is applicable to be fabricated using dilute electrodeposition at room temperature with low thermal oxidation process.