Single-crystalline van der Waals layered dielectric with high dielectric constant.

The scaling of silicon-based transistors at sub-ten-nanometre technology nodes faces challenges such as interface imperfection and gate current leakage for an ultrathin silicon channel. For next-generation nanoelectronics, high-mobility two-dimensional (2D) layered semiconductors with an atomic thickness and dangling-bond-free surfaces are expected as channel materials to achieve smaller channel sizes, less interfacial scattering and more efficient gate-field penetration. However, further progress towards 2D electronics is hindered by factors such as the lack of a high dielectric constant (κ) dielectric with an atomically flat and dangling-bond-free surface. Here, we report a facile synthesis of a single-crystalline high-κ (κ of roughly 16.5) van der Waals layered dielectric BiSeO. The centimetre-scale single crystal of BiSeO can be efficiently exfoliated to an atomically flat nanosheet as large as 250 × 200 μm and as thin as monolayer. With these BiSeO nanosheets as dielectric and encapsulation layers, 2D materials such as BiOSe, MoS and graphene show improved electronic performances. For example, in 2D BiOSe, the quantum Hall effect is observed and the carrier mobility reaches 470,000 cm V s at 1.8 K. Our finding expands the realm of dielectric and opens up a new possibility for lowering the gate voltage and power consumption in 2D electronics and integrated circuits.