Asymmetric Chemical Functionalization of Top‐Contact Electrodes: Tuning the Charge Injection for High‐Performance MoS<sub>2</sub> Field‐Effect Transistors and Schottky Diodes
Bin Han, Yuda Zhao, Chun Ma, Can Wang, Xinzi Tian, Ye Wang, Wenping Hu, Paolo Samorı́
Abstract
Abstract The fabrication of high‐performance (opto‐)electronic devices based on 2D channel materials requires the optimization of the charge injection at electrode–semiconductor interfaces. While 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 has not been demonstrated for the top‐contact configuration, despite the latter being known to offer enhanced charge‐injection characteristics. Here, a novel contact engineering method is developed to functionalize gold electrodes in top‐contact field‐effect transistors (FETs) via the transfer of chemically pre‐modified electrodes. The source and drain Au electrodes of the molybdenum disulfide (MoS 2 ) FETs are functionalized with thiolated molecules possessing different dipole moments. While the modification of the electrodes with electron‐donating molecules yields a marked improvement of device performance, the asymmetric functionalization of the source and drain electrodes with different molecules with opposed dipole moment enables the fabrication of a high‐performance Schottky diode with a rectification ratio of ≈10 3 . This unprecedented strategy to tune the charge injection in top‐contact MoS 2 FETs is of general applicability for the fabrication of high‐performance (opto‐)electronic devices, in which asymmetric charge injection is required, enabling tailoring of the device characteristics on demand.