  Rectifying semiconductor junctions are crucial to electronic devices. They
convert alternating current into direct one by allowing unidirectional charge
flows. In analogy to the current-flow rectification for itinerary electrons,
here, a polar rectification that based on the localized oxygen vacancies (OVs)
in a Ti/fatigued-SrTiO3 (fSTO) Schottky junction is first demonstrated. The
fSTO with OVs is produced by an electro-degradation process. The different
movability of localized OVs and itinerary electrons in the fSTO yield a
unidirectional electric polarization at the interface of the junction under the
coaction of external and built-in electric fields. Moreover, the fSTO displays
a pre-ferroelectric state located between paraelectric and ferroelectric
phases. The pre-ferroelectric state has three sub-states and can be easily
driven into a ferroelectric state by external electric field. These
observations open up opportunities for potential polar devices and may underpin
many useful polar-triggered electronic phenomena.
