Atomically-thin HfSe2 transistors with native metal oxides

HfSe2 is a layered semiconductor relevant for two-dimensional (2D) field effect transistors (FETs), with recent reports of a bulk band-gap comparable to Silicon (Eg ~ 1.1 eV) [1,2] and oxidation into the high-K insulator HfO2 [1,3]. However, extreme environmental sensitivity has prevented device measurements in samples below bulk (~ 20 nm) thickness [3]. Here, we present the first systematic study of HfSe2 devices, including joint computational and spectroscopic elucidation of its electronic band structure, characterization of ambient degradation, and transport measurements down to carefully encapsulated trilayers. Transistors fabricated in inert atmospheres and capped with AlOx are long-term air-stable, with comparable performance to other 2D dichalcogenide semiconductors (Ion/Ioff ~ 106, current densities ~30 μA/μm) but offering native integration with high-K HfOx dielectrics.