Latest advance on seamless metal-semiconductor contact with ultralow Schottky barrier in 2D-material-based devices

2D-material semiconductors with unique photonic and optoelectronic properties process ultralow energy consumption and are naturally compatible to semiconductor fabrication process, which show great potential in many applications such as memristors, optoelectronic probers, energy devices, and catalytic system. Generally, electrode fabrication process inevitably introduces a non-Ohmic contact between the semiconductor and its electrodes due to the Schottky barrier and gap states, thus raising energy consumption and limiting device performance. Recently, seamless-contact technologies have been developed, which can turn the semiconductor-electrode contact to be Ohmic by eliminating gap states and Schottky barrier, thereby having fundamental implications on 2D-material-based devices. This work will review the recent progresses of the seamless contacts from both theory and experiment aspect, summarize the existing difficulties, exploring improvement of metal-semiconductor contact and propose future exploration direction. This review is timely and helpful to improve the performance of 2D-material-based devices by introducing seamless contact and approaching the Ohmic contact.