Giant charge trapping in 2D layered oxide nanosheets via intrinsic quantum wells

Abstract

The atomically thin nature of two-dimensional (2D) layered materials makes them susceptible to charge trapping by randomly created disorders, adversely affecting carrier dynamics such as charge transport and exciton lifetime. Typically, these disorders lead to poor device performance or require additional space to mitigate performance degradation. In this study, we investigate 2D layered Dion–Jacobson (DJ)-phase oxide perovskite nanosheets, which exhibit charge trapping within their well-defined quantum well (QW) structures, resulting in unique tailoring of electrical conductivity and photoconductivity. These DJ-phase perovskites, composed of tunable atomic constituents, demonstrate resonant tunneling and anomalous charge trapping due to their ultra-clean QWs. Remarkably, the conductivity of insulating HSr₂Nb₃O₁₀ (HSNO) increased over 1000 times upon applying voltage without additional treatments. We observed persistent photoconductivity in 2D vertical heterostructure devices, attributed to charge trapping in QWs, and demonstrated artificial synaptic behaviours in a single flake with tailored energy consumption. Varying the number of perovskite layers significantly allows the tunability of the energy bandgap. This study also highlights the high tunability of 2D perovskite nanosheets, promising various applications, including magnetic, high-k dielectric, and resistive switching devices. Our findings suggest a new class of ionic layered materials with great potential as novel two-dimensional building blocks for device applications.