Synthesis of 2D Nonlayered α‐Nb₂O₅ Nanosheets by the Growth Promoter of Sulfur and Alkali Halides

Niobium‐based oxides with wide bandgap and high dielectric constant show great potential in the applications of electronic and optoelectronic devices. Herein, the quasi‐van der Waals epitaxial growth of 2D α‐Nb 2 O 5 nanosheets is reported, in which the growth promoter of sulfur and alkali halides has been utilized to catalyze the ultrathin 2D growth. The relatively low Gibbs free energy of α‐Nb 2 O 5 nanosheets can drive the ultrathin growth down to 30 nm on the c‐Al 2 O 3 substrate by the transformation of T‐Nb 2 O 5 powder sources without any doping effects, demonstrating the diverse α‐Nb 2 O 5 nanostructure morphologies. The as‐grown α‐Nb 2 O 5 nanosheets are characterized with high crystalline quality and specific dominated growth plane, indicating the uniform dielectric properties. The metal–insulator–metal capacitor has confirmed the α‐Nb 2 O 5 nanosheet with a high dielectric constant over 40. The dual promoters’ growth design strategy provides a universal synthesis method for the 2D nonlayered dielectric materials.