Resistance Switching Behaviors And Nb-doped Properties In BiFeO₃Thin Films

Research on ferroelectric is undergoing a heated research stage. Some ferroelectrics with perovskite structures like Pb(Zr1-xTix)O3, BaTiO3have been extensively studied. BiFeO3has received broad attention attributing to its high Cure temperature. Recently, the widely used flash storage can not keep up with the progress of time due to the limits in size and energy consumption. Thus, searching for a memory material with high integration, low energy consumption and fast response will be critical in such an era of information explosion.This paper mainly studies two aspects of work:(1) research the resistance switching behavior of BiFeO3thin film deposited by pulsed laser deposition,(2) study the semiconductor and multiferroic properties of Nb doped BiFeO3thin film. As follows:(1) Ferroelectric BiFeO3and paraelectric Bi0.8Ca0.2FeO3polycrystalline films were prepared to study the dependence of resistive switch on defect density. With defect density and the corresponding leakage current increasing, current-voltage loops allow four different types, i.e., overlapping, hysteresis without memory effect, bipolar resistive switch, and unipolar resistive switch. The first three types can transform to the last one, once electroforming introduces enough charged defects to films and the resistance monotonically increases to a certain value. Unipolar resistive switch is due to conductive filamentary type and can be treated as an especial electroforming process. Furthermore, its high resistance status allows the second or third type at low voltage region.(2) Structural changes of doped BiFeO3can result in the variation of physical properties e.g. ferroelectric and piezoelectric, attracting wide studies nowadays. We study the variation of conductivity and piezoelectric properties in Nb-doped BiFeO3. Fortunately, we find that with the increase of Nb, BiNbFeO3alters from insulator to semiconductor, companying by an increase in conductivity. Thus, the ferroelectric and piezoelectric of BiNbFeO3are difficult to measure due to the high leakage current.We researched the resistance switching behavior of BiFeO3thin film and confirmed that the bipolar and unipolar resistance switching behavior can be measured at the same time. Finally, Nb was doped into the BiFeO3thin film to translate it from insulator to semiconductor.