Reversible and rewritable p- and n-type conducting ferroelectric domain walls?

Can we make reversibly rewritable p-and n-type conducting ferroelectric domain walls (DWs) by controlling point defect populations? This question is motivated by the prospect of multi-level DW-based diodes and memristive DWs which could be reversed, erased, and re-written by a combination of thermoatmospheric history (annealing) and locally applied electric fields (e.g. from a scanning probe). Density functional theory (DFT) calculations are here used to evaluate the potential of two classes of uniaxial ferroelectrics, improper ferroelectric hexagonal manganites and hyperferroelectric LiNbO₃. Specifically, the potential of relying on local oxygen excess or deficiency, or accumulation of protons, is investigated by DFT calculations of point defects and derroelectric DWs. Compared to point defects at metal cation lattice sites, oxygen and hydrogen defects possess the major advantages that they are both relatively spatially mobile and readily exchanged with the surrounding atmosphere at mildly elevated temperatures. Finally, experimental challenges will be briefly discussed along with the anticipated potential of other well studied ferroelectric materials.