The Mechanism Investigation Of ZnO Nanorods-based Resistive Memory

ZnO nanorods have shown a significant value in electronic and optoelectronic devices due to its wide band gap, easy synthesis and excellent optical performance. It is considered that it is suitable for the electrons moving in one dimension because the carrier confinement in the other dimensions. In recent years, the resistive memory devices based on Zn O nanorods have been reported. However, there exist the dissatisfied parameters and controversial mechanism. The Zn O nanorods array were prepared and then the discussion of surface modification on device performance was performed. Also the device structure and switching mechanism are concerned. The main conclusion is as the following:1. ZnO nanorods with various diameters were prepared by chemical bath deposition technique under elevated temperature. The mechanism of current conduction and resistive switching for device structure of ITO/Zn O NRs/Al was discussed by the current-voltage curve and bias-dependent fluorescence spectroscopy. The dominant conduction mechanisms for the two resistance states are concluded to be ohmic and space charge limited current conduction,respectively. We confirmed that the increased oxygen vacancies density under forward bias establishes the conductive path for the electron transportation. As the result, the switching from the high resistance state to the low resistance state is achieved. Under reverse voltage,the high resistance state was re-obtained with the paths broken off.2. The PbS quantum dots were synthesized by using the hot injection method and then were spin-coated on the as-prepared Zn O nanorods for Zn O/Pb S heterojunction formation.Compared with the device without Pb S, the ON/OFF ratio was increased by about 20 times.The influence of Pb S modification is evaluated and described as the barrier reduction between Zn O and Pb S from the accumulation of interface oxygen vacancies. With aid of conductive filaments, the device is switched from the high resistance state to the low resistance state. The conductive filament is ruptured by oxygen vacancies reduction under negative bias, inducing the switching back to high resistance state.3. An electronic bistable device with a hybrid structure was fabricated by coating carbon quantum dots(C QDs) into the tapered Zn O nanorod array. With the addition of C QDs, the ON/OFF ratio was found to be as high as 103, which is over 100 times larger than the corresponding value in non-containing C QDs device. The effect of C QDs on the resistive switching behavior and its mechanism were investigated by current-voltage and capacitance-voltage characterization. From the linear fitting results of current density-voltage characteristics curves in log-log scale, the resistive switching mechanisms of the two devices can be described by space charge limited current. In addition, the device yield is increased to90% by C QDs filling the gap between nanorods.