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.