Control of threshold voltage by gate metal electrode in molybdenum disulfide field-effect transistors

Abstract

This study reports the control of threshold voltage (Vth) by engineering a gate metal electrode in molybdenum disulfide (MoS2) field-effect transistors (FETs). The fabrication process for gate stacks involves the deposition of aluminum oxides (AlOx) on a high-work-function metal and the subsequent formation of a self-assembled monolayer (SAM) by an immersion method. A positive Vth of 0.15 V was demonstrated using a platinum (Pt) metal as a gate electrode accompanied by a low density of traps at the interface owing to the close-packed SAM. Raman spectroscopy revealed that the transferred MoS2 has a multi-layer structure. The Pt gate electrode exhibits a Vth shift of about 1 V in the positive direction compared with the aluminum (Al) gate electrode. This Vth shift is consistent with the difference in the work function of Pt and Al gate metal electrodes. The low–temperature process employed in this study makes it possible to assemble dissimilar materials including the Pt metal, deposited AlOx, and organic SAM molecules to manipulate the Vth in MoS2 FETs. This work is expected to open up intriguing directions for research on the applications and developments of functional FETs based on two-dimensional materials.