Advances in dielectric performance of atomically engineered perovskite nanosheet thin films

The search for new high-performance dielectric material receives continued research interest. Several mechanisms for high permittivity have been proposed such as BaTiO3-based perovskites or CaCu3Ti4O12. Nevertheless, developing thin films with such high performance remains a highly challenging task. However, reducing the BaTiO3-based film thickness raises the leakage current and suppresses dielectric responses because of a low-permittivity interfacial ‘dead-layer’. Here, we propose a new materials design route to great permittivity behavior in atomically-thin films, where charge engineering of layered perovskites generates giant polarizability and results in 2-dimensional materials with colossal permittivity. Firstly, we present a concrete example Dion-Jacobson type KSr2 − xBixNb3O10 and its cation-exchanged form HSr2 − xBixNb3O10, which exhibit a stable colossal permittivity and a low dielectric loss. Also, Sr2(1−x)Bi2xNb3O10 (x = 0.1) nanosheets attain by chemical exfoliation method with a high dielectric permittivity of over 500, the highest among all known dielectrics in the ultrathin films (< 20 nm). As Bi-substitution of Sr2Nb3O10, the dielectric permittivity exhibits two times higher value due to higher polarizability of Bi ions and leads larger dielectric permittivity. Density functional theory calculations suggest that the substitution of high-valent Bi ions with lone pairs are responsible for the colossal permittivity. Our results provide a strategy for achieving new high-k nanodielectrics for use in nano-scaled electronics.