Surface functionalization toward top-gated monolayer MoS2 field-effect transistors with ZrO2/Al2O3 as composite dielectrics

Abstract

Growth of high-k dielectrics on two-dimensional (2D) materials is vital for the fabrication of electronic and optoelectronic devices. In this work, the uniform high-k ZrO2 dielectric thin films were successfully grown by atomic layer deposition (ALD) on monolayer MoS2 with Al2O3 buffer layers. No significant variations appear for MoS2 after deposition of Al and ZrO2 thin films. The properties of composite dielectrics on MoS2 films have been studied by Cr-Au/ZrO2/Al2O3/MoS2 Metal-oxide-semiconductor (MOS) devices, in which H2O and O3 were used as the oxidants for ZrO2 growth, respectively. Moreover, the top-gated monolayer MoS2 field-effect transistors (FETs) with ZrO2/Al2O3 as composite dielectrics have been successfully fabricated. Importantly, the top-gated structure gives the transistors with a high mobility of 11.14 cm2 V−1 s−1, a high on/off-state current ratio of 107 at VDS = 0.1 V, a small subthreshold swing of 0.93 V dec−1, and a proper threshold voltage of 2.29 V. Hence, the integration of the high-k dielectrics on MoS2 develops the possibilities to prepare high-performance top-gated FETs based on 2D materials.