Scalable Synthesis of High-Quality Ultrathin Ferroelectric Magnesium Molybdenum Oxide

The development of ultrathin, stable ferroelectric materials is crucial for advancing high-density, low-power electronic devices. Nonetheless, ultrathin ferroelectric materials are rare due to the critical size effect. Here, a novel ferroelectric material, magnesium molybdenum oxide (Mg₂Mo₃O₈) is presented. High-quality ultrathin Mg₂Mo₃O₈ crystals are synthesized using chemical vapor deposition (CVD). Ultrathin Mg₂Mo₃O₈ has a wide bandgap (≈4.4 eV) and nonlinear optical response. Mg₂Mo₃O₈ crystals of varying thicknesses exhibit out-of-plane ferroelectric properties at room temperature, with ferroelectricity retained even at a 2 nm thickness. The Mg₂Mo₃O₈ exhibits a relatively large remanent polarization ranging from 33 to 52 µC cm^{- 2}, which is tunable by changing its thickness. Notably, Mg₂Mo₃O₈ possesses a high Curie temperature (>980 °C) across various thicknesses. Moreover, the as-grown Mg₂Mo₃O₈ crystals display remarkable stability under harsh environments. This work introduces nolanites-type crystal into ultrathin ferroelectrics. The scalable synthesis of stable ultrathin ferroelectric Mg₂Mo₃O₈ expands the scope of ferroelectric materials and may prosper applications of ferroelectrics.