Continuous Control of Charge Transport in Bi - Defi cient BiFeO 3 Films Through Local Ferroelectric Switching

It is demonstrated that electric transport in Bi-defi cient Bi 1− δ FeO 3 ferroelectric thin fi lms, which act as a p-type semiconductor, can be continuously and reversibly controlled by manipulating ferroelectric domains. Ferroelectric domain confi guration is modifi ed by applying a weak voltage stress to Pt/ Bi 1− δ FeO 3 /SrRuO 3 thin-fi lm capacitors. This results in diode behavior in macroscopic charge-transport properties as well as shrinkage of polarization-voltage hysteresis loops. The forward current density depends on the voltage stress time controlling the domain confi guration in the Bi 1− δ FeO 3 fi lm. Piezoresponse force microscopy shows that the density of head-tohead/tail-to-tail unpenetrating local domains created by the voltage stress is directly related to the continuous modifi cation of the charge transport and the diode effect. The control of charge transport is discussed in conjunction with polarization-dependent interfacial barriers and charge trapping at the non-neutral domain walls of unpenetrating tail-to-tail domains. Because domain walls in Bi 1− δ FeO 3 act as local conducting paths for charge transport, the domain-wall-mediated charge transport can be extended to ferroelectric resistive nonvolatile memories and nanochannel fi eld-effect transistors with high performances conceptually.