Ferroelectric Tunnel Junctions: Resistive Switching Behavior by Scanning Probe Microscopy

In this work, we demonstrate the reproducible tunneling electroresistance effect in ultrathin epitaxial ferroelectric heterostructures by means of scanning probe microscopy techniques. Ultrathin films of barium titanate (in the range from 2 nm to 10 nm) with microscopically patterned SrRuO3 top electrodes have been grown on the SrRuO3/SrTiO3 substrates by atomic-layer-controlled pulsed-laser deposition. Imaging and control of polarization state in SrRuO3/BaTiO3/SrRuO3 and BaTiO3/SrRuO3 heterostructures have been performed via Piezoresponse Force Microscopy (PFM) along with conductance measurements by Conducting Atomic Force Microscopy (C-AFM). The selected locations have been probed by performing the local I-V measurements using a fixed tip. In parallel, at the same locations local PFM hysteresis loops have been measured. The obtained results show a change in resistance by about two orders of magnitude upon polarization reversal on a lateral scale of 20 nm at room temperature. These results are promising for employing ferroelectric tunnel junctions in non-volatile memory and logic devices.