Preparation And Memristor Properties Of Titania And Zirconia Films And Their Heterojunctions

In the era of rapid development of microelectronic devices.Due to the influence of microscopic effects such as quantum tunneling and capacitive coupling,the development of traditional flash semiconductor memory is hindered.Therefore,the research of new memory is significant for the future development of memory field,as a substitute for traditional memory,the emergence of a variety of emerging memories has been widely concerned,Such as Resistive random access memory,Ferroelectric random access memory,Magnetic random access memory,Phase change random access memory and so on.Among them,resistive random access memory(RRAM)has become a research hotspot in recent years due to its considerable miniaturization.RRAM has fast response speed,simple structure,high density,high speed and low power consumption.It is also compatible with CMOS technology and has three-dimensional integration capability which made it hopeful to break Moore's law.Many breakthroughs have been made in the research of RRAM in recent years.However,there are still many objections to its principle,the resistance mechanism mainly includes metal conductive filament or oxygen vacancy filament,but there is still no theory can explain the formation condition of conductive filament and the performance of resistive switching perfectly,in this paper,two kinds of popular and reliable metal oxides,ZrO₂ and TiO₂,have been studied.They have excellent chemical stability,simple preparation process,rich content of titanium and zirconium in the earth's crust,and the preparation cost is low.Moreover,ZrO₂and TiO₂ are harmless to the environment and human body,which conform to the concept of green,healthy and sustainable environmental protection.The top metal/dielectric layer/bottom electrode was used as the basic device structure,and TiO₂ or ZrO₂ films were deposited on conductive substrates by sol-gel method.The memristor properties of the single film were systematically studied,and the memristor property of the TiO₂/ZrO₂ heterojunction structure was also studied.The experimental results show that when PT is used as the bottom electrode for both TiO₂ and ZrO₂ thin films,the response speed of the device is faster,the working current is higher and the threshold voltage is lower the write voltage(even if the device changes from high resistance state to low resistance state)and erase voltage(the voltage that makes the device change from low resistance state to high resistance state)have large fluctuation,and the overall anti fatigue performance of the device is poor.However,the devices using FTO or ITO as the bottom electrode have slower response speed,smaller operating current and larger threshold voltage,but the overall stability and small floating.No matter which substrate is used,the fatigue phenomenon will appear in the continuous testing process,that is,the working current of the device fluctuates,and the ratio of high and low resistance to states decreases until the resistance switching phenomenon disappears.The R_HRS/R_LRS ratio of the samples annealed in nitrogen atmosphere is significantly higher than that of the samples annealed in oxygen atmosphere.The memristor properties of oxide films with different thickness are different.The fatigue resistance of the devices can be significantly improved by using heterojunction structure.The performance of the device is mainly determined by the voltage applied on the film to regulate the carrier.Therefore,it is of great significance to study the various conductive mechanisms of the thin film for the design and application of the device.There are two kinds of conductive mechanisms in dielectric materials,i.e.electrode limited conduction mechanism and volume limited conduction mechanism.Based on the experimental data,we transform the values of voltage and current,and then determine the conductive mechanism of the device through the linear relationship between the transformed voltage and current,and then study the resistance mechanism of the film.