Scalable Synthesis of High‐Quality Ultrathin Ferroelectric Magnesium Molybdenum Oxide

Abstract 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 (Mg 2 Mo 3 O 8 ) is presented. High‐quality ultrathin Mg 2 Mo 3 O 8 crystals are synthesized using chemical vapor deposition (CVD). Ultrathin Mg 2 Mo 3 O 8 has a wide bandgap (≈4.4 eV) and nonlinear optical response. Mg 2 Mo 3 O 8 crystals of varying thicknesses exhibit out‐of‐plane ferroelectric properties at room temperature, with ferroelectricity retained even at a 2 nm thickness. The Mg 2 Mo 3 O 8 exhibits a relatively large remanent polarization ranging from 33 to 52 µC cm − 2 , which is tunable by changing its thickness. Notably, Mg 2 Mo 3 O 8 possesses a high Curie temperature (>980 °C) across various thicknesses. Moreover, the as‐grown Mg 2 Mo 3 O 8 crystals display remarkable stability under harsh environments. This work introduces nolanites‐type crystal into ultrathin ferroelectrics. The scalable synthesis of stable ultrathin ferroelectric Mg 2 Mo 3 O 8 expands the scope of ferroelectric materials and may prosper applications of ferroelectrics.