Rectifying semiconductor-ferroelectric polarization loops and offsets in Pt-BaTiO3-ZnO-Pt thin film capacitor structures

Electrical and polarization hysteresis measurements on Pt-BaTiO3-ZnO-Pt heterostructures, grown by pulsed laser deposition on (001)Si, are reported. The layers were deposited without breaking the vacuum using a switchable target holder. Offsets of hysteresis loops along the polarization axis with increasing sweeping voltage, time-dependent charging, and rectifying behavior are observed. A simple electrical circuitry can be used to model the observed hysteresis behavior, where the interface between the wurtzite-structure ZnO and the pervoskite-structure BaTiO3 is seen as the origin of a space charge accumulation region. Coupling between spontaneous wurtzite and switchable ferroelectric polarization is discussed.