Performance Investigation of Multilayer MoS2 Thin-Film Transistors Fabricated via Mask-free Optically Induced Electrodeposition.

Abstract

Transition metal dichalcogenides, particularly MoS2, have recently received enormous interest in explorations of the physics and technology of nanodevice applications because of their excellent optical and electronic properties. Although monolayer MoS2 has been extensively investigated for various possible applications, its difficulty of fabrication renders it less appealing than multilayer MoS2. Moreover, multilayer MoS2, with its inherent high electronic/photonic state densities, has higher output driving capabilities and can better satisfy the ever-increasing demand for versatile devices. Here, we present multilayer MoS2 back-gate thin-film transistors (TFTs) that can achieve a relatively low subthreshold swing of 0.75 V/decade and a high mobility of 41 cm2·V-1·s-1, which exceeds the typical mobility value of state-of-the-art amorphous silicon-based TFTs by a factor of 80. Ag and Au electrode-based MoS2 TFTs were fabricated by a convenient and rapid process. Then we performed a detailed analysis of the impacts of metal contacts and MoS2 film thickness on electronic performance. Our findings show that smoother metal contacts exhibit better electronic characteristics and that MoS2 film thickness should be controlled within a reasonable range of 30-40 nm to obtain the best mobility values, thereby providing valuable insights regarding performance enhancement for MoS2 TFTs. Additionally, to overcome the limitations of the conventional fabrication method, we employed a novel approach known as optically induced electrodeposition (OIE), which allows the flexible and precise patterning of metal films and enables rapid and mask-free device fabrication, for TFT fabrication.