| BiFeO3(BFO)is used as a basis for multifunctional materials and devices,which possesses ferroelectricity and ferromagnetism at room temperature.However,high leakage current and large coercive field have become obstacles to technological development and application.Ion doping has been proved to reduce leakage current.The construction of ferroelectric oxide heterojunctions has been found to be a new research area,and has attracted the attention of a large number of researchers due to the heterostructures formed and the broad development prospects.In this work,Bi0.9Er0.1Fe1-xMnxO3(BEFMxO)thin films,Bi0.9-yLayEr0.1Fe0.96Co0.02Mr0.02O3(BLayEFMCO)thin films,Bi0.9Er0.1Fe0.99 Mn0.01O3/Zn1-zCuzO(BEFM/ZCuzO)composite films and Bi0.89La0.01Er0.1Fe0.96 Mn0.02Co0.02O3/Zn1-wCuwO(BLEFMC/ZCuwO)composite films are synthesized by sol-gel technique.The effects of ion doping on the crystal structure,defects,leakage mechanism,ferroelectricity,and ferroelectric stability were analyzed.The effects of compounding semiconductor oxide layer on the structure,ferroelectric,and resistance switching behavior of the composite thin films were further studied.The results are as follows:(1)The structure,electrical properties and ferroelectric stability of BEFMxO films were studied.The trigonal phase R3c:H and R3m:R two phases coexist,the generation of oxygen vacancies is suppressed,and the leakage current density is reduced by Mn ion-doping.BEFO exhibits mainly electron tunneling and poor polarization stability under an increased applied electric field.However,the BEFMxO(x=0.01-0.03)films show a small oxygen vacancy concentration and is dominated by bulk conduction which have less effect on ferroelectric domain switching,and the BEFM0.02O film shows excellent ferroelectric stability.(2)The morphology,ferroelectricity and ferromagnetism of BLayEFMCO films were studied.La doping can induce grain size refinement of the films.The leakage current conduction mechanism works together with ohmic and space charge conduction,and oxygen vacancies and defects play a leading role.The ferroelectric property of the BLa0.01EFMCO film is enhanced,and the renmant polarization and switching current are 152μC/cm2 and 1.50 mA,respectively.As the doping amount of La ions increases,the pinning effect of defects on ferroelectric domains and the formation of a large built-in electric field inside the film weaken the ferroelectric polarization.However,the BLa0.09EFMCO film shows enhanced magnetic properties.(3)The structure,ferroelectricity and resistive switching behavior of BEFM/ZCuzO composite films are studied.Three phases of BFO,Bi2Fe4O9 and ZnO coexist in the composite films,and BFO phase undergoed a transition from trigonal R3c:H to triclinic P1.The BEFM/ZnO film shows obvious diode rectification effect and ferroelectricity,but the ferroelectricity and diode effect of the BEFM/ZCuzO composite films disappear,and the resistance switching effect is weakened.(4)The structure,ferroelectricity and resistive switching behavior of BLEFMC/ZCuwO composite films were investigated.The BLEFMC/ZCu0.01O composite thin film possesses enhanced ferroelectricity,exhibiting the largest remanent polarization value and switching current at the same applied voltage.At the same time,it shows good ferroelectric stability and anti-breakdown characteristic.Ion co-doping of upper and lower can improve the resistance switching behavior of the composite films.The switching ratio of BLEFMC/ZCu0.05O film reaches 22.4. |
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