Ferroelectric behavior of ultra-thin BiFeO$_{3}$ films*

BiFeO$_{3}$ (BFO) is a potential oxide-barrier material for spintronics devices like magnetic tunnel junctions. Also, recent theoretical predictions have opened up the possibility of realizing multi-level devices with ferroelectric (FE) barriers. But understanding the FE properties of ultra-thin BFO films is at its early stages. Control over FE domains with robust polarization switching is a challenge and crucial for achieving any device-related objectives. In this work we have investigated the FE domains of BFO films of thickness between 5 - 100 nm using peizo-force microscopy (PFM) technique, and local properties using switching spectroscopy PFM (SS-PFM). Our films show significant polarization switching loops down to 5nm. We find domains to be irregular-shaped, in sharp contrast to thicker films. Detailed analysis shall be presented.