Controlled Growth of Bilayer‐MoS2 Films and MoS2‐Based Field‐Effect Transistor (FET) Performance Optimization

Abstract The effect of hydrogen flow on MoS 2 film synthesis via chemical vapor deposition is studied systematically. Large‐sized monolayer‐ and bilayer‐MoS 2 triangles can be synthesized controllably at given temperatures. Optical microscopy, Raman spectroscopy, photoluminescence spectroscopy, and atomic force microscopy are used to characterize the number of layers, purity, and uniformity of the MoS 2 triangle films. Moreover, the back‐gated field‐effect transistors (FETs) based on the monolayer‐ and bilayer‐MoS 2 channels are fabricated using traditional micro‐nanoprocessing technology. Electrical behaviors are investigated and the bilayer‐MoS 2 FETs show preferable performance with high mobility (≈21 cm 2 V −1 s −1 ), on‐current (≈22 µA µm −1 ), and a small degradation in the on/off ratio (1.1 × 10 7 ). Finally, the semiconductive phase MoS 2 (2H‐MoS 2 ) is transformed to a metallic phase (1T‐MoS 2 ) to reduce the resistance in metal‐MoS 2 contact. The FET device with 1T‐MoS 2 contact enhances mobility (≈45 cm 2 V −1 s −1 ) and on‐current (≈50 µA µm −1 ) compared with the 2H‐MoS 2 FETs. This work sheds light on the synthesis of variable‐layer MoS 2 films and paves the way for further development regarding MoS 2 film‐based devices.