Boosting Carrier Mobility and Restoring Ambipolarity in 2D TMD Transistors via Nano-spherical Probe Cleaning.

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDs), particularly MoS2 and WSe2, are ideal candidates for constructing next-generation high-performance electronics due to their atomic thickness and excellent electrical tunability. However, interface contaminants and bubbles inevitably introduced during device fabrication remain a critical challenge, acting as scattering centers that severely limit carrier mobility and induce device instability. This study demonstrates an in situ mechanical contact strategy using a nano-spherical probe to precisely remove interface residues in MoS2/hBN and WSe2/hBN van der Waals heterostructures. Experimental results indicate that this method significantly reduces interface roughness from ∼11.5 to ∼1.35 nm. The cleaned MoS2 field-effect transistors (FETs) exhibited a significant increase in effective electron mobility from ∼8.5 to 79.2 cm2/V·s, an improvement of approximately one order of magnitude in the on/off ratio, and a significant suppression of charge-trapping-induced hysteresis. For WSe2 devices, the technique successfully restored intrinsic symmetric ambipolar transport characteristics, enhancing both electron and hole drive currents. Furthermore, a 90-day monitoring period in a non-vacuum environment revealed the different degradation mechanisms of interface adsorbates on n-type and p-type carrier transport. This work not only confirms the universality of nanomechanical cleaning technology in enhancing the intrinsic performance of 2D material heterostructure devices but also deeply elucidates the structure-property relationship regarding long-term stability, providing guidance for the interface engineering of high-performance 2D electronics.