Mcirostructural and electrical properties of ferroelectric/ZnO heterostructures

The microstructural and electrical properties of ferroelectric/ZnO heterostructures fabricated on SrTiO3 substrates by pulsed laser deposition (PLD) were investigated. Reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) were employed to characterize the orientation of the samples. On ferroelectric oxide surfaces of (001) and (111) orientations, both of ZnO films followed c-axial direction. For the former, twin-domain structure would result in a smaller mismatch of about -1% by the epitaxial relation of ZnO[110]//BaTiO3 < 110 >. On (111) surfaces, single-domain ZnO films were observed with the in-plane orientation ZnO[100]//BaTiO3[110] although 30 degrees domain rotation in the in-plane direction of the ZnO epilayer respect to the perovskite surfaces induced very large mismatch of about -15%. The allepitaxial metal-ferroelectric-semiconductor (MFS) structures of ZnO/Pb(Zr0.52Ti0.48)O-3/SrRuO3 were deposited on SrTiO3(111) substrates due to the cube-on-cube epitaxial relationship between ferroelectric, SrRuO3 electrode and substrates. Capacitance-voltage (C-P) measurements showed a ferroelectric window, indicating that the structures can achieve memory performance. The improvement of MFS inversion characteristics could be mainly due to good ferroelectric/ZnO interface.