field effect transistors via selectively deposited thiol-molecules*

Although two-dimensional (2D) molybdenum disulfide (MoS₂) has gained huge attention due to its unique physical properties, the limited electrical contact to 2D semiconductors still impedes to realize high-performance MoS₂-based devices. In this regard, many studies have been conducted to improve the injection properties by inserting tunneling layers, such as hexagonal boron nitride or graphene, between MoS₂ and electrodes.[1,2] However, the reported strategies require relatively low-yield and time consuming transfer processes on MoS₂ flakes. Here, we suggest a simple contact modification method, introducing chemically adsorbed thiol molecules as thin tunneling barriers between the metal electrodes and MoS₂ channels. The directly deposited thiol-molecules via the vapor-deposition process introduce additional tunneling paths at the contact regions, improving the carrier injection properties with lower activation energies in MoS₂ field-effect transistors. Additionally, by inserting thiol-molecules at the only one contact region, asymmetric carrier-injection was feasible depending on the temperature and gate bias.
[1] Wang, J. et al. Adv. Mater. 28, 8302-8308 (2016)
[2] Cui, X. et al. Nano Lett. 17, 4781-4786 (2017)