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.