2D-MoS2/BMN Ceramic Hybrid Structure Flexible TFTs with Tunable Device Properties.

Abstract

Two-dimensional (2D) layered semiconductor materials have emerged as prospective channel materials in flexible thin-film field effect transistors (TFTs) recently because of their unique electrical and mechanical characteristics. Meanwhile, high-quality ceramics, with outstanding dielectric property and fabrication process compatible with low-cost flexible substrates, have become one of the best candidates of gate dielectric layers in flexible TFTs. In this work, 2D MoS2 and dielectric ceramic Bi2MgNb2O9 (BMN) were utilized to fabricate flexible TFTs on low-cost polyethylene terephthalate substrates. The MoS2/BMN hybrid structure exhibited good quality by Raman, X-ray photoelectron spectroscopy, and atomic force microscopy characterizations. In addition, the flexible MoS2/BMN TFTs indicated good performances with a small gate voltage. More importantly, with the modulation of gate voltage, the flexible TFTs surprisingly exhibited three different device types, that is, multilayer MoS2/BMN n-type TFT (device type 1), homojunction MoS2/BMN TFT (device type 2), and thick MoS2/BMN p-type TFT (device type 3). In particular, with different bias conditions, the homojunction TFT showed bipolarity of transfer characteristics and forward/backward rectifications of output characteristics similar to p-n/n-n junctions. The high dielectric constant and high quality of the BMN ceramic layer enabled the gate to effectively modulate these different structures of MoS2 channels. The operation mechanisms of these three types of flexible TFTs were investigated. Additionally, the flexible MoS2/BMN TFTs showed good flexibility and performance stability with external strains. The results prove the great potential of integration of 2D materials, high-quality dielectric ceramics, and low-cost plastic substrates for high-performance flexible TFTs and further applications of flexible electronics.