Two-dimensional (2D) materials as channel materials provide a promising alternative route for future electronics and flexible electronics, but the device performance is affected by the quality of interface between the 2D-material channel and the gate dielectric. Here we demonstrate an indium selenide (InSe)/hexagonal boron nitride (hBN)/graphite heterostructure as a 2D field-effect transistor (FET), with InSe as channel material, hBN as dielectric, and graphite as gate. The fabricated FETs feature high electron mobility up to 1,146 cm²·V^-1·s^-1 at room temperature and on/off ratio up to 10¹⁰ due to the atomically flat gate dielectric. Integrated digital inverters based on InSe/hBN/graphite heterostructures are constructed by local gating modulation and an ultrahigh voltage gain up to 93.4 is obtained. Taking advantages of the mechanical flexibility of these materials, we integrated the heterostructured InSe FET on a flexible substrate, exhibiting little modification of device performance at a high strain level of up to 2%. Such high-performance heterostructured device configuration based on 2D materials provides a new way for future electronics and flexible electronics.

We use Z-contrast imaging and atomically resolved electron energy-loss spectroscopy on an aberration-corrected scanning transmission electron microscope to investigate the local electronic states of boron atoms at different edge structures in monolayer and bilayer hexagonal boron nitride (h-BN). We find that edges with bonding unsaturated sp² boron atoms have a unique spectroscopic signature with a prominent pre-peak at ~ 190.2 eV in the B K-edge fine structure. First-principles calculations reveal that the observed pre-peak arises from excitations to the in-plane lowest-energy empty sp² boron dangling bonds at the B-terminated edge. This spectroscopic signature can serve as a fingerprint to explore new edge structures in h-BN.