Ultra-low Voltage Resistive Switching Characteristics Of Fe-doped SrTiO₃ Film

With the rapid development of high-tech industries such as Internet of Things,supercomputers,5G communications and big data analysis applications.In order to meet requiements of human society for ultra-fast reading/writting speed,high storage density,small size and low energy consumption,various new types of non-volatile memory devices have been explored in the laboratory.Resistive switching random access memory?RRAM?has simple structure and excellent matching relationship between switching speed and energy consumption.It is suitable for next generation of non-volatile memory and artificial synaptic components.Sr TiO₃?STO?film is a good candidate material for RRAM devices.Our literature investigation shows that switching voltages of RRAM devices based on STO films are usually greater than1 V,and most of them need necessary forming process to exhibit resistive switching behavior.High/low resistance ratios of STO-based RRAM devices can be significantly improved by introducing various point defects into STO film,where Sr or Ti ions are partially replaced by those doped metal atoms.However,it has no significant improvement for device's endurance and retention properties.Inserting metal/oxide buffer layer between STO film and electrodes can improve endurance and retention properties,but switching voltages are increased while high/low resistance ratios have no significant improve.In this paper,about 3 at.%Fe atoms are doped in the STO film,which heavily affects concentration of oxygen vacancy defect in the STO film,switching voltages reduce less than 1 V,high/low resistance ratios and endurance properties are obviously improved.Fe-doped STO film?Fe-STO?is prepared by RF magnetron sputtering as the resistive switching layer material.Pt and Ag are chosen as electrode materials to form a RRAM cell with the Ag/Fe-STO/Pt sandwich structure.Effects of film thickness,deposition temperature and bottom electrode material on device resistive switching characteristics were explored.Resistive switching mechanism of Fe-STO film was also discussed.Experimental results show that the Fe-STO film deposited at 450?with a thickness of about 80 nm exhibits excellent resistive switching characteristics:the high/low resistance ratio is greater than 10⁵,the Set/Reset voltage is reduced to±0.6 V,and the Reset voltage has a narrower distrubition.The RRAM cell can work stably for more than 2500 cycles,and has good device repeatability.Fe-STO films deposited at 600?exhibit three different resistive switching patterns.Different surface topography of Ag bottom layer causes the RRAM cell exhibit unipolar or threshold-type resistive switching behaviors.Fe atoms make the STO film is heavily oxygen deficient,which facilitates the formation of oxygen vacancy conductive filaments,thereby greatly reduces switching voltages.Fe-STO film has shown potential applications in new type of low power consumption,multilevel resistive switching RRAM cells suitable for artificial neural synapes.