The tape exfoliation method is still the easiest and most convenient way to obtain large-area two-dimensional (2D) monolayers in experimental research. Recently, there are some important advances in tape exfoliation method for large 2D monolayer materials. This review mainly introduced three kinds of new tape exfoliation methods including modified Scotch tape exfoliation method, metal-assisted tape exfoliation method and gel-assisted tape exfoliation method. We highlight the operation process and exfoliated mechanism of each method. We point out several problems to be solved and give an outlook on the development direction of the new tape exfoliation method. We hope this review will help researchers, especially for beginners, quickly and easily obtain a variety of 2D monolayers for their own experiments.

materials has attracted extensive attention in nanoelectronics devices. [1][2][3] Among the large studies on various 2D semiconductor materials, MoS 2 as a transition metal chalcogenides is a credible candidate for channel materials in the future metal-oxide-semiconductor field-effect transistors (MOSFET) because its unique advantages such as suitable bandgap (1.2-1.9 eV), [4] high field-effect mobility (40 cm 2 V -1 s -1 on average), [5] and large on-off ratio (up to 10 8 ). [6][7][8] In addition, MoS 2 MOSFET with the atomic thickness is itself the structure of silicon on insulating layer, which can eliminate the floating body and improve the subthreshold slope. Therefore, the 2D MoS 2 is widely used to research short-channel MOSFET. [9][10][11] In short-channel MOSFET devices, the power consumption is particularly influenced by high contact resistance (R c ) at the metal/semiconductor interfaces. [12,13] In order to reduce the power consumption and increase transmission current, the Ohmic contact is an important factor for 2D MoS 2 MOSFET because it can significantly lower the additional impedance.Compared to the total resistance, the ideal Ohmic R c is relatively small. Hence, the voltage drop across the ideal Ohmic R c The formation ofOhmic contact between metal electrode and 2D semiconductor channel is considered a key factor for performance improvement of 2D metal-oxide-semiconductor field-effect transistors (MOSFET). However, the Schottky barrier at the metal electrode/2D semiconductor interfaces cannot be lowered effectively due to the pinning effect of Fermi levels, which makes it hard to obtain lower Ohmic contact resistance. Until now, although physical transfer metal electrode or inserted tunneling layer has been reported to get rid of the Fermi-level pinning effect, these different designs of electrode engineering are not systematically compared. To serve better Ohmic contact, three different designs of electrode engineering are employed in 2D MoS 2 MOSFET: evaporating Ag electrode on MoS 2 , transferring MoS 2 to Ag electrode, and inserting ultrathin AlO x tunneling layer. Our experimental results demonstrate that the transferring MoS 2 to Ag electrode in 2D MoS 2 MOSFET can obtain the lowest contact resistance and Schottky barrier of 0.45 Ωcm and 12.8 meV, respectively. On this basis, photodiodes with obvious rectifying behavior are fabricated using schemes of electrode engineering, due to their different Schottky barrier high. The detailed contrastive analysis in our three different designs of electrode engineering can provide valuable guidance to optimize the performance of 2D semiconductor MOSFET.

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