Ferroelectric properties of YMnO3 epitaxial films for ferroelectric-gate field-effect transistors

Abstract

Ferroelectric properties of YMnO3 epitaxial films were studied. The ferroelectric properties of epitaxially grown (0001) YMnO3 films on (111)Pt/(0001)sapphire (epi-YMO/Pt) with an excellent crystallinity were compared to (0001)-oriented poly crystalline films on (111)Pt/ZrO2/SiO2/Si. The epi-YMO/Pt had saturated polarization–electric-field (P–E) hysteresis loops, with a remanent polarization (Pr) of 1.7 μC/cm2 and a coercive field (Ec) of 80 kV/cm. The fatigue property showed no degradation up to 1010 measured cycles. These results suggested that the YMnO3 epitaxial films were suitable ferroelectric material for the ferroelectric-gate field-effect transistors. Consequently, epitaxially grown (0001)YMnO3 films on epitaxial Y2O3/Si (epi-YMO/Si) were fabricated. The epi-YMO/Si capacitor had almost equivalent crystallinity compared to epi-YMO/Pt. It was recognized that the epi-YMO/Si capacitor exhibited the ferroelectric type C–V hysteresis loop with the width of the memory window of 4.8 V, which was almost identical to the value of twice coercive voltage of the P–E hysteresis loops of the epi-YMO/Pt. A retention time exceeding 104 s was obtained in the epi-YMO/Si capacitor.

Epitaxial growth of multiferroic YMnO3 on GaN

“…Both YMnO 3 and GaN have hexagonal symmetry and have a nominal lattice mismatch of about 4% (to half the lattice constant of YMnO 3 ). We observe an unexpected 30° rotation between the two unit cells, resulting in a much larger lattice mismatch of ~10 %.…”

“…We observe an unexpected 30° rotation between the two unit cells, resulting in a much larger lattice mismatch of ~10 %. To understand these results, we have carried out first principles calculations of the elastic energy of highly strained YMnO 3 . Because the relative stability of the first 1-2 layers determines the orientation of subsequent layers, we focus our calculations on the first unit cell at the interface.…”

“…Recently, thin films of YMnO 3 have been grown epitaxially on Si (111) [3][4]. These structures have been proposed for use in nonvolatile memory devices, taking advantage of the ferroelectric properties of YMnO 3 as well as its chemical stability at high temperatures.…”

Epitaxial growth of biferroic YMnO3(0001) on platinum electrodes

“…Moreover, towards the integration of ferroelectric YMO into devices, epitaxial films onto suitable bottom electrodes must be developed. Indeed, Ito et al [5] have earlier reported the epitaxy of YMO(0 0 0 1) films on Pt(1 1 1)/Al 2 O 3 (0 0 0 1). Although the polarization P(E) loops of these films were better that those of polycrystalline YMO films, squarer P(E) loops are required [5].…”

“…Indeed, Ito et al [5] have earlier reported the epitaxy of YMO(0 0 0 1) films on Pt(1 1 1)/Al 2 O 3 (0 0 0 1). Although the polarization P(E) loops of these films were better that those of polycrystalline YMO films, squarer P(E) loops are required [5]. Film microstructure plays a fundamental role on the ferroelectric properties and detailed structural studies on hexagonal YMO hexagonal films is still lacking.…”