Ambipolar Memristive Phenomenon in Large-Scale, Few-Layered αMoO₃ Recrystallized Films

Studies of two-dimensional (2D) oxide materials are not common, primarily because of the difficulty in obtaining crystal sizes large enough to fabricate devices structures from exfoliation of bulk crystals. Among the layered oxide materials, alpha molybdenum trioxide (αMoO₃) is of particular interest because of its wide bandgap and high hole mobility. Here the growth of highly uniform, large-scale, ambipolar, few-layered αMoO₃ that is appropriate for nanofabrication is reported. Crystal grain sizes on the order of 5 µm are observed across samples as large as 10 × 10 mm² with hexagonal grain boundaries and surface roughness of less than 500 pm rms. Exact [010] crystal orientation, characteristic of the layered atomic structure αMoO₃, is observed. The measured bandgap energy is ≈2.8 eV. Carrier mobilities in polycrystalline films are and 2.28 cm² V⁻¹ s⁻¹ (hole) and 3.18 cm² V⁻¹ s⁻¹ (electron) at room temperature in air. Simple field-effect device structures are characterized by ambipolar carrier transport producing memristive device characteristics, which is attributed to a polarization field produced by the strong coupling between electron and phonons in these crystals.