Two-Dimensional Transition-Metal Dichalcogenides — from Material, Physics to Devices

Atomically thin two dimensional (2D) transition-metal dichalcogenides (TMDCs) are attracting high interests lately due to novel quantum properties as well as the ultimate miniaturization in thickness that promises nano-electronics. These 2D semiconductors have a novel multi-valley band structure where electrons are labeled by the spin and valley pseudo-spin, offering ideal platforms to explore new concept logic devices by exploiting these internal degrees of freedom as information carriers. Their visible frequency range band gap (1.5 ~ 1.9 eV) is also ideal for electronics and optoelectronics.
Bulk TMDCs exist in the form of stacks of strongly bonded atomic layers attracted by the much weaker van der Waals force. Exfoliation of single layer TMDC for a 2D flake sample is possible by micromechanical cleavage (e.g., using Scotch tape) and by intercalation by lithium ions, for example. Using the “flake” samples, people have already made interesting and important discoveries about the properties of the 2D materials, promising for future spin electronic and valley electronic applications. Moreover, prototype devices have been made to demonstrate the concepts of using 2D semiconductor in electronic devices. However, because the flake samples are usually small and not very reproducible, explorations of such materials are greatly hindered. There is a demand of better and large sized TMDC samples for characterization and for device applications.
In this proposal, we bring together a team of active researchers in this front of research for a concerted and timely effort aiming at: (1) producing high quality large sized 2D TMDC samples and novel devices based on the materials; and (2) exploring spin and valley related new physics for new concept devices. The different expertise of the team members and a combination of theory and experimental study will ensure a comprehensive and productive project, leading to new findings that likely impact on the advancement of nano-electronics and nano-optoelectronics.