Ultrathin Hafnium Oxide Integration for Two-Dimensional Functional Electronic Devices

Two-dimensional (2D) materials are considered promising candidates for next-generation electronic devices, especially field-effect transistors (FETs). However, deposition of a uniform dielectric layer on 2D materials with an inert surface is challenging. Herein, the integration of HfO_<i>x</i> on graphene is demonstrated through simple thermal oxidation of HfS₂ precursor to form a high-quality HfO_<i>x</i>/graphene stack. The thermal treatment enables complete conversion from HfS₂ into ultrathin HfO_<i>x</i> with an atomically smooth surface and sharp interface with graphene. The transformed thin HfO_<i>x</i> shows decent dielectric properties, including a high dielectric constant of 18 and a robust breakdown field of 10 MV/cm. High-performance MoS₂ FETs based on HfO_<i>x</i>/graphene gate stack demonstrate a high ON/OFF ratio of 10⁶, a low subthreshold swing of 75 mV/dec, and a low leakage current. Resistive switching devices were also fabricated showing coexistence of volatile and nonvolatile switching, and a steep switching slope. This nondestructive integration of high-quality high-κ dielectrics on 2D materials opens up possibilities for developing multifunctional 2D electronics.