Study On Preparation And Properties Of ZnMn₂O₄Resistive Switching Thin Films And P-n Hetero-junction

As computers, mobile phones, MP3,and other portable personal equipments were gradually popular, non-volatile memory plays an increasingly important role in the semiconductor industry. Resistive random access memory (RRAM) is considered one of the most promising candidates for the next generation of non-volatile memory devices due to storage unit structure is simple, high-speed performance, low power, information remained stable, non-volatility, compatible with CMOS technology and High integration density. It is likely to replace DRAM, SRAM and Flash to be a universal memory.TE/ZnMn2O4/BE (TE:top electrode, BE:bottom electrode) sandwich structure is prepared by Sol-gel technique (preparation ZnMn2O4resistance layer) and magnetron sputtering (preparation electrode). The crystalline structure of the thin film was characterized by X-ray diffraction (XRD, AXS D8-ADVANCE, Brucker). The surface and cross-section morphologies were observed with a scanning electron microscope (SEM, Hitachi S4800). Current-Voltage (Ⅰ-Ⅴ) curves were obtained with a Keithley2400digital source meter. The influence of resistance layer thickness, annealing temperature, TE, BE, and Cu or Fe doping was discussed. The main contents and achievements are as follows:(1) Thickness and annealing temperature have a significantly effect on the Ag/ZnMn2O4/p++-Si structure resistive switching device. It was observed that the Vresetof the devices increased with the increase of ZnMn2O4layer thickness and the Vset voltage showed weak dependence on film thickness. Furthermore,255nm thick ZnMn2O4film was proved to have the best resistive switching characteristics. It’s Vset and Vreset distribution is concentrated in the2.5～3V and-3～-4V, respectively. The resistance and grain sizes of ZnMn2O4film increased with the increase annealing temperature. The Vreset and Vreset of the device have no obvious change with the annealing temperature increase.(2) TE and BE have an significant effect on Conductive type, mechanism and the resistance characteristics of the TE/ZnMn2O4/BE structure resistive switching devices. A typical bipolar Ⅰ-Ⅴ characteristics was observed in TE/ZnMn2O4/p++-Si hetero-junction devices. The resistive switching exhibits two types of conduction mechanisms, LRS and HRS, which are dominated by conduction filaments and SCLC, respectively. After1000switching cycles, Ag/ZnMn2O4/p++-Si devices have the best resistance to fatigue properties. TE/ZnMn2O4/Pt devices have typical unipolar Ⅰ-Ⅴ characteristics. Ag/Cu/ZnMn2O4/Pt devices have the minimal and concentrated operating voltage. After100switching cycles, it’s also having a better resistive switching characteristic. Disappointingly, TE/ZnMn2O4/n++-Si device have no switching characteristics. (3) The Cu, Fe doping has different effect on the TE/ZnMn204/BE structure devices.As Cu doped, Zni.xCuxMn204iflm grain was increase evidently. Grain size is the largest,when doping amount x=0.10. The resistance characteristic Resistance performance andfatigue properties of the device were decreased with Cu doped. Fe doped make the grain ofZnMn2.yFey04films more small evidently, and the grain size decreases with the increasingof doping amount, when doping amount y=0.10and y=0.20, the Roff/Ron had obviousincrease to1056and10, respectively, Fe doped also did not improve the stability andresistance to fatigue characteirstics.