Resistance Switching Induced By Interfacial Phase Change In Oxide Heterojunction

With the development of information technology,as a new type of non-volatile memory,ferroelectric memory has the advantages of low power consumption,good duration and easy regulation.But ferroelectric memory is also facing some problems,such as the leakage current of ferroelectric materials is too large,the difference between high and low resistance states is too small.Therefore,it is expected that ferroelectric polarization reversal can induce the accumulation and dissipation of holes in LSMO at the interface,so as to trigger the phase change of LSMO and to make the ON/OFF ratio of ferroelectric memory more obvious,the resistance performance of ferroelectric memory can be improved.In this paper,high quality La_1-xSr_xMnO₃?x = 0,0.15,0.2,0.3?films were prepared by pulsed laser deposition.By changing the substrate temperature of PZT film,uniform and high quality PZT films were prepared.The effect of PZT film thickness on ferroelectric properties and resistance properties of Pt/PZT/LSMO heterojunction was studied.When the thickness of PZT film is 72 nm,the leakage current density of PZT film in the heterojunction is low and the ferroelectric performance of PZT film is good.Next,La_0.7Sr_0.3MnO₃ and PZT/La_0.7Sr_0.3MnO₃ films were prepared,and the transition temperatures of their metal-insulation phases were measured to be 330 K and 250 K,it indicates that the polarization reversal of PZT can regulate the phase change of LSMO.On this basis,by changing the screened layer LSMO in ferroelectric heterojunction,the Pt/PZT/La_1-xSr_xMnO₃?x = 0,0.15,0.2,0.3?/La_0.7Sr_0.3MnO₃ ferroelectric heterojunctions were designed and fabricated.The ferroelectric properties of four heterojunctions were studied,the hysteresis loop of the four heterojunctions is in the saturated state,and the polarization intensity was the same,indicating that the difference in the resistance performance between the four heterojunctions was independent of ferroelectricity.The resistance behavior of four heterojunctions was tested by setting different scan voltages,we can obtain the ON/OFF ratio of Pt/PZT/La0.8Sr0.2Mn O3/La_0.7Sr_0.3MnO₃ is the largest,which is 7.2×104,and the difference between positive and negative voltage is the most obvious,this is because the screened layer La0.8Sr0.2Mn O3 is at the critical point of ferromagnetic metal state and ferromagnetic insulation state,ferroelectric polarization reversal can induce the accumulation and dissipation of holes in the La0.8Sr0.2Mn O3 film at the interface,thus trigger the crossing of La0.8Sr0.2Mn O3 between the critical point and improve the resistance performance of the heterojunction;the ON/OFF ratio of Pt/PZT/La_0.7Sr_0.3MnO₃ is 7×104;the ON/OFF ratio of Pt/PZT/La0.85Sr0.15 Mn O3/La_0.7Sr_0.3MnO₃ was significantly reduced,and the maximum ON/OFF ratio is 4×104;the maximum ON/OFF ratio of Pt/PZT/La Mn O3/La_0.7Sr_0.3MnO₃ can only reach 103,this is because the LMO film is in an anti-ferromagnetic insulation state at room temperature.The reliability test of four heterojunctions was carried out,and the four heterojunctions all can erase continuously and have good data retention.