Integration of Ultrathin Hafnium Oxide with a Clean van der Waals Interface for Two-Dimensional Sandwich Heterostructure Electronics

Integrating high-κ dielectrics with a small equivalent oxide thickness (EOT) with two-dimensional (2D) semiconductors for low-power consumption van der Waals (vdW) heterostructure electronics remains challenging in meeting both interface quality and dielectric property requirements. Here, we demonstrate the integration of ultrathin amorphous HfO_x sandwiched within vdW heterostructures by the selective thermal oxidation of HfSe₂ precursors. The self-cleaning process ensures a high-quality interface with a low interface state density of 10¹¹-10¹² cm^-2 eV^-1. The synthesized HfO_x displays excellent dielectric properties with an EOT of ∼1.5 nm, i.e., a high κ of ∼16, an ultralow leakage current of 10^-6 A/cm², and an impressively high breakdown field of 9.5 MV/cm. This facilitates low-power consumption vdW heterostructure MoS₂ transistors, demonstrating steep switching with a low subthreshold swing of 61 mV/decade. This one-step integration of high-κ dielectrics into vdW sandwich heterostructures holds immense potential for developing low-power consumption 2D electronics while meeting comprehensive dielectric requirements.