In-situ TEM observation of Multilevel Storage Behavior in low power FeRAM device

The quest for non-volatile memories has attracted tremendous attention, especially in mature ferroelectric random access memory (FeRAM) with properties of high read/write speed and low power consumption. Strain engineering of multiferroic BiFeO3 (BFO) has recently become the subject of broad research interest because of its intriguing properties. In this study, we demonstrate the switchable diode characteristics in highly strained BFO thin films. Using a unique in situ electrical transmission electron microscopy (TEM), we verify the correlation between ferroelectric resistive switching with multilevel states and polarization reversal. Structural investigation confirms that the phase transition from mixed phase to pure T-like phase, accompanying with the polarization reversal by external bias, is the origin of the multilevel states. The switchable diode with multilevel resistive switching can be explained in terms of the variation of the barrier height, governed by ferroelectric polarization and polarity of the external bias. This research model, i.e., engineering of the room inside, can offer an approach toward high-density memories.