Study On Ferroelectric Resistive Switching Behavior Of Pb?Zr,Ti?O₃/?La,Sr?MnO₃ Heterostructures

Ferroelectric/semiconductor heterostructures,due to the interaction of lattice,charge,orbit,and spin at the interface,have special interface effects,rich and unique physical properties,and have good application prospects in the fields of photoelectric,energy storage and information storage.However,the interface effects of ferroelectric/semiconductor heterostructures and the inevitable connection between ferroelectricity and resistive switching behavior have not been fully understood.Besides,the performances of ferroelectric resistive switching?RS?devices are still too poor to satisfy the practical application.In this work,epitaxial PbZr_0.52Ti_0.48O₃?PZT?ferroelectric thin films were grown on Nb-doped SrTiO₃?NSTO?single-crystal substrates by pulsed laser deposition.moreover,La_0.67Sr_0.33MnO₃?LSMO?layers with different thicknesses were constructed between the interface of PZT and NSTO.By constructing an insertion layer between the ferroelectric layer and the substrate,not only improve RS performance but also benefit for understanding the RS mechanism.The regulation of resistance switching behavior and micro-mechanism of PZT/LSMO/NSTO heterostructures were investigated.The main research contents and conclusions are as follows:LSMO films with different thicknesses were fabricated on the STO substrates,the stress state of LSMO films was comprehensively analyzed by reciprocal space mapping.the results show that the stress relaxation thickness of the LSMO film is about 51 nm,and the growth rate of LSMO film is about 2.5 nm/min;PZT films with different thicknesses were fabricated on Nb:STO substrates,and it is found that the built-in electric field formed at the interface of PZT/NSTO heterojunction can pin the ferroelectric domains in the PZT film near the interface of PZT/NSTO,resulting in P-E hysteresis loops present obvious asymmetry.In addition,the growth rate of the PZT film is found to be 5 nm/min.A LSMO ultrathin layer with a thickness of 7 nm is inserted into the PZT/NSTO heterostructures.The results show that the P-E hysteresis loops of PZT/NSTO heterostructures present obvious asymmetry,and the RS ratio can reach 10³orders of magnitude.However,by inserting the LSMO layer,the P-E hysteresis loops became relatively symmetric,but the RS effect almost disappeared.It can be considered that the LSMO layer affect the interfacial energy band structures of the PZT/NSTO heterostructures,which makes ferroelectric polarization lose its effect on the modulation of the depletion layer width.Therefore,the existence of the initial depletion layer is very important for the RS effect of ferroelectric/semiconductor heterostructures.The effect of LSMO insertion layer thickness on the RS behavior of PZT/LSMO/NSTO heterostructures was also investgated.By changing the thickness of LSMO insertion layer,the RS ratio can be regulated.The results show that the maximum ON/OFF ratio up to 1770can be obtained in the PZT/LSMO/NSTO heterostructure with the 140 nm thick LSMO layer.It is found that the ferroelectric polarization can regulate the width of the depletion layer at the LSMO/NSTO interface and the oxygen vacancy concentration in the heterostructures.