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.

The transfer of graphene from metallic substrates onto application-specific substrates is usually inevitable for the applications of high-quality graphene films derived from chemical vapour deposition (CVD) approaches. Commonly used to support the graphene films during the transfer, the coating of the polymer would produce the surface contaminations and hinder the industrially compatible transfer. In this work, through the thermal imidization of polyamide acid (PAA) to polyimide (PI) and tuning of the concentration of dangling chains, we achieved the ultraclean and crack-free transfer of graphene wafers with high electronic quality. The resulting contamination-free and hydrophilic surface also enabled the observed improved cell viability in a biomedical applications. By avoiding aqueous etching or the usage of strong bases, our proposed transfer method is industrially compatible for batch transfer of graphene films towards the real applications.

Chemical vapor deposition (CVD) has emerged as a promising approach for the controlled growth of graphene films with appealing scalability, controllability, and uniformity. However, the synthesis of high-quality graphene films still suffers from low production capacity and high energy consumption in the conventional hot-wall CVD system. In contrast, owing to the different heating mode, cold-wall CVD (CW-CVD) system exhibits promising potential for the industrial-scale production, but the quality of as-received graphene remains inferior with limited domain size and high defect density. Herein, we demonstrated an efficient method for the batch synthesis of high-quality graphene films with millimeter-sized domains based on CW-CVD system. With reduced defect density and improved properties, the as-received graphene was proven to be promising candidate material for electronics and anti-corrosion application. This study provides a new insight into the quality improvement of graphene derived from CW-CVD system, and paves a new avenue for the industrial production of high-quality graphene films for potential commercial applications.

Chemical vapor deposition (CVD)-grown graphene films on Cu foils, exhibiting fine scalability and high quality, are still suffering from the adverse impact of surface contamination, i.e., amorphous carbon. Despite the recent successful preparation of superclean graphene through Cu-vapor-assisted reactions, the formation mechanism of amorphous carbon remains unclear, especially with regard to the functions of substrates. Herein, we have found that the crystallographic orientations of underlying metal substrates would determine the cleanness of graphene in such a way that slower diffusion of active carbon species on as-formed graphene-Cu(100) surface is the key factor that suppresses the formation of contamination. The facile synthesis of clean graphene is achieved on the meter-sized Cu(100) that is transformed from the polycrystalline Cu foils. Furthermore, a clean surface of graphene on Cu(100) ensures the reduction of transfer-related polymer residues, and enhanced optical and electrical performance, which allows for versatile applications of graphene in biosensors, functioning as flexible transparent electrodes. This work would offer a promising material platform for the fundamental investigation and create new opportunities for the advanced applications of high-quality graphene films.