Construction of High Field-Effect Mobility Multilayer MoS₂ Field-Effect Transistors with Excellent Stability through Interface Engineering

Abstract

Electrical stability and field-effect mobility of two-dimensional (2D) material-based field-effect transistors (FETs) are extremely important for practical electronic applications. Interface scattering during the transmission of 2D materials, which can be significantly influenced by the interface between dielectric and 2D materials, remains a formidable challenge. Early work has achieved excellent mobility and on/off ratio, but the understanding and improvement of the electrical stability of MoS2 devices are still in their infancy. Herein, a facile and effective strategy is proposed via a spin-coated polymethyl methacrylate (PMMA) dual layer to enhance both field-effect mobility and electrical stability of molybdenum disulfide (MoS2) FETs, in which the PMMA underneath MoS2 works as a gate dielectric together with SiO2 and the PMMA on top of MoS2 is used to protect the FET channel from exposure to air. The field-effect electron mobility has been improved up to 2.5 times, from 41.8 to 104.6 cm2/Vs, by using PMMA/SiO2 as the back gate dielectric and PMMA capsulation layer. The time- and stress-dependent electrical stability has been essentially improved. A negligible threshold voltage shift (ΔVth < 0.1 V) and field-effect mobility degradation (1.4%) are achieved upon a gate bias voltage of ±35 V applied for 300 s, even after 45 day storage in open air. The effective suppression of interface impurities located at the channel interface contributes to the electrical performance enhancement of MoS2 FETs. Furthermore, a theoretical model was developed to investigate different MoS2/dielectric interface structures by density functional theory (DFT), which is consistent with interface scattering theory. This study not only provides a clue for the high-performance 2D FET fabrication but also offers an opportunity to understand the electrical property degradation mechanism of the 2D material family devices, pushing forward their practical applications in the 2D devices and flexible electronics.