Resistance-containing The Bi Compounds Of Ferroelectric Thin Films Varying Characteristics And Ferroelectric Domain Lateral Movement

Ferroelectric memories have attracted significant attentions in past years for the advantages of fast writing/reading speed, low power consumption, and high-density integration. However, the capacitor based memories have some shortcomings. The area of the capacitors is too large to scale them up to gigabit density devices, and a restoring pulse is required after a destructive readout. Recently, the non-destructive readout of the binary information is possible from the bipolar switching between high- and low- conductance of a ferroelectric diode under two opposite polarization directions. Such memory has many important properties, such as the ultrafast operating speed depending on the polarization flipping time and the high ratio of resistance in the forward and reverse directions.Most of the resistive switching effects are based on a certain type of defect (ionic or electronic) mediated phenomenon. So it is difficult to control the switching behavior in precise. On the contrary, ferroresistive switching behavior is based on the intrinsic switching of ferroelectric domains without invoking of charged defect migration. As a result, it may possess an essential merit over defect-mediated mechanisms for achieving reliable performance requisite for commercial production.In this work, BiFeO3/SrRuO3/SrTiO3 structure was developed. With the performance of piezoresponse force microscopy (PFM) and conductive atomic force microscope (C-AFM), we confirmed that ferroelectricity and conductivity coexisted in a single phase, and the conductivity was modulated by ferroelectricity.In high-density 1T1C-type ferroelectric random access memories, each memory cell can be formed with the crossed regions of two sets of parallel bars of top and bottom electrodes with the 90°rotation. During reading and writing cycles, a cell capacitor is polarized by giving a bias between selected top and bottom electrode bars in the latter. The peripheral region of the selected element beyond electrode coverage could also be switched under the writing/reading pulse. To avoid this crosstalk problem between adjacent memory cells, the safe distance between adjacent elements was estimated for Pt/SrBi2Ta2O9/Pt thin-film capacitors with different cell sizes. Polarization fatigue under different frequencies and voltages were also measured for the memory with increased integration density.