Observation of nanoscopic charge-transfer region at metal/MoS₂ interface

2D materials are promising for next-generation device applications, such as flexible transistors. However, the devices using 2D materials as active layers cannot exhibit good performance. One of the causes is that electronic properties are influential to the interface with, for instance, metal contact due to an ultra-thinness of the 2D materials. We have, therefore, performed core-level photoelectron microscopy measurements to investigate the local electronic states at interfaces in a MoS₂ field-effect transistor (FET). We detect a charge-transfer region (CTR) at the MoS₂/metal-electrode interface, which expands over ∼500 nm with the electrostatic potential (energy shift) variation of ∼70 meV, which causes band bending in the MoS₂ electronic structure with a Fermi level shift. The observed potential variation of the CTR is well reproduced by a simple calculation using Poisson's approximation. Our results point to a potential way of understanding the interfacial effect of the MOS₂/metal electrode on the device characteristics and performance. (paper)