LAUSR

The fabrication of high-performance (opto-)electronic devices based on ultrathin two-dimensional channel materials requires the optimization of the charge injection at the electrode - semiconductor interface. While the chemical functionalization with chemisorbed self-assembled monolayers has been extensively exploited to adjust the work function of metallic electrodes in bottom-contact devices, such a strategy was never demonstrated when the top-contact configuration is chosen, despite the latter is known to offer enhanced charge injection characteristics. Here, we have developed a novel contact engineering method to functionalize gold electrodes in top-contact field-effect transistors (FETs), via the transfer of chemically pre-modified electrodes. The source and drain electrodes of the molybdenum disulfide (MoS2 ) FETs were functionalized with prototypical thiolated molecules possessing by design different dipole moments. While the modification of the Au electrode with electron-donating molecules yielded a marked improvement of the device performance, the asymmetric functionalization of the source and drain electrodes with two different chemisorbed molecules with opposed dipole moment enabled the fabrication of a high-performance Schottky diodes with a rectification ratio of ∼103 . Our unprecedented strategy to tune the charge injection and extraction in in top-contact MoS2 FETs is of general applicability for the fabrication of high-performance opto-electronic devices based on 2D semiconductors in which the energetic asymmetry is required to boost the device functionality (e.g., for light-emitting transistors, solar cells, etc), enabling to tailor the device characteristics on-demand. This article is protected by copyright. All rights reserved.