Towards wafer-scale growth of two-dimensional cerium dioxide single crystal with high dielectric performance

Owing to the atomically thin nature, two-dimensional (2D) oxide materials have been widely reported to exhibit exciting transport and dielectric properties, such as fine gate controllability and ultrahigh carrier mobility, that outperform their bulk counterpart. However, unlike the successful synthesis of bulk oxide single crystals, reliable methods for synthesizing large-area single crystal of 2D oxide, that would suppress the negative influence from defective grain boundaries, remain unavailable, especially for nonlayered oxide. Herein, we report that the lattice symmetry between the substrate and cerium dioxide (CeO₂) would allow for the aligned nucleation and epitaxial growth of CeO₂ on sapphire substrates, enabling the wafer-sized growth of CeO₂ single crystal. The careful tuning of the growth temperature and oxygen flow rate contributed to the harvesting of CeO₂ wafer with reduced thickness and enhanced growth rates. The removal of grain boundaries improved the dielectric performance in terms of high dielectric strength (E_bd ≈ 8.8 MV·cm^–1), suppressed leakage current, along with high dielectric constants (ε_r ≈ 24). Our work demonstrates that with fine dielectric performance and ease of synthesizing wafer-sized single crystals, CeO₂ can function as potential candidate as gate insulator for 2D-materials based nanoelectronics, and we believe the reported protocol of aligned nucleation can be extended to other 2D oxides.