Ferroelectricity of YMnO3 Thin Films on Pt(111)/Al2O3(0001) and Pt(111)/Y2O3(111)/Si(111) Structures Grown by Molecular Beam Epitaxy

Abstract
Ferroelectric YMnO 3 (YMO) thin films were grown on Pt/Al2O3 (0001) and Pt/Y2O3/Si (111) structures using Y2O3 buffer layers by molecular beam epitaxy (MBE). In situ reflection high-energy electron diffraction (RHEED) analyses and X-ray diffraction (XRD) analyses showed that both Y2O3 and YMO films were epitaxially grown on both substrates. Capacitance–voltage (CV) measurement for a YMO film on the Pt/Al2O3 structure showed a butterfly-type curve with a memory window of 0.85 V. The remanent polarization (2Pr) of the film was determined to be larger than 0.7 µC/cm2 from Sawyer-Tower measurement. Ferroelectricity of a YMO film in the Al/YMO/Y2O3/Pt/Y2O3/Si(111) structure was almost the same as that on Pt/Al2O3, which indicated that the effect of the different thermal expansion coefficients of the substrates was not significant.