Van der Waals integrable high- <i>κ</i> HfO <i> _x </i> dielectric for two-dimensional transistors

Abstract Two-dimensional (2D) semiconductor materials are considered as promising candidates for next generation field-effect transistors (FETs). However, the dielectric properties and the interface quality between the 2D semiconductors and dielectric hinder the realization of the full potential of 2D FETs. In this work, we demonstrate the van der Waals integrable high- κ HfO x dielectric by chemically converting 2D semiconducting HfS 2 via ultraviolet ozone treatment. By measuring the dielectric properties of the Au/HfO x /Au capacitor, an electric breakdown field of ∼8.9 MV cm −1 , dielectric constant of ∼9.6 and ultralow leakage current of ∼10 −5 A cm −2 can be achieved. Back-gate MoS 2 transistors with HfO x as the gate dielectric show a current on/off ratio of ∼10 9 and electron mobility of ∼ 35.3 cm 2 ·V −1 ·s −1 . Top-gate MoS 2 transistors with HfO x as the gate dielectric exhibit a subthreshold swing of ∼80.2 mV dec −1 , indicating the efficient gate control and minimal interface trap states in the MoS 2 channel between the 2D MoS 2 channel and the high- κ HfO x dielectric. When using HfO x as the tunneling layer in floating-gate transistors, the devices show a large memory window of up to 14 V, a current on/off ratio of ∼10 8 , data retention time of exceeding 8000 s, and endurance over 350 cycles. These results demonstrate that the van der Waals integrable high- κ HfO x facilitate the construction of high-quality dielectrics on 2D materials to enhance overall device performance.