Integration of Air-Sensitive 2D Monolayers for High Performance vdW Heterostructure-Based Devices and Their Optoelectronic Properties

Two-dimensional (2D) transition metal dichalcogenides are of great interest for electronic and optoelectronic applications; however, integrating them into devices remains challenging due to issues such as disorders, strains, and high contact resistance. This challenge is particularly severe for air-sensitive monolayers like MoTe2 and WTe2 as degradation is unavoidable when using conventional methods. However, universal integration techniques for air-sensitive monolayers are underdeveloped, limiting the investigation and development of their potential for electronics and quantum technologies.
Here, we will first present novel integration techniques that can be universally applied to air-sensitive monolayers, including both semiconductors and semimetals. We will showcase this approach using 2H-MoTe2, which has recently attracted significant attention for its exotic topological states in twisted bilayers, and 1T’-WTe2, known for its superconductivity at monolayer limits. These monolayers are perfectly sealed by fluorinated graphene throughout the entire process, ensuring protection while also improving charge transmission between 3D metal contacts and the monolayers, resulting in enhanced performance. This approach demonstrates a two-orders-of-magnitude reduction in contact resistance and long-term stability for both MoTe2 and WTe2.
Next, we will present results demonstrating ohmic contact at cryogenic temperature for MoTe2 monolayer, which is necessary for the precise investigation of quantum phases. By leveraging work function-induced charge transfer, we selectively doped the MoTe2 monolayer and achieved record-high mobility. Last but not least, we will focus on the stacking faults in dielectric hBN layers, which are easily formed during the fabrication of vdW heterostructures. These stacking faults are often overlooked due to their invisibility in optical microscope and atomic force microscopy. We will explain how these stacking faults can affect the vdW heterostructure and their overall performance.
This presentation will broaden the potential of vdW heterostructures for improved stability and performance and create new opportunities for exploring exciting physics in air-sensitive materials.