Transfer assembly for two-dimensional van der Waals heterostructures

Two-dimensional (2D) van der Waals (vdW) heterostructures with pre-determined properties are key ingredients for the success of advanced electronics and optoelectronics. The construction of vdW heterostructures is a prerequisite to obtain the desired performance with high quality. A typical dry/wet transfer technique is a promising route to physically stack vdW heterostructures via a gentle-energy fabrication procedure, allowing the fabrication of atomically sharp and thin heterointerfaces. This strategy has gained considerable attention for intriguing physics phenomena such as superconductivity, topological insulator, valleytronics, and interweaving proximity effect. It also offers various possibilities to construct sophisticated electrical, optical, energy harvesting, and memory devices. Here, we review the state-of-the-art transfer techniques and describe their advantages and drawbacks. We also discuss the transfer methodologies of particular purposes, which are extremely desired for further exploration of the vdW heterostructures such as the integration of diverse functional substrates, passivation of air-sensitive materials, twistronics, vdW contacts by 3D metal, and hybrid devices with 1D or 3D materials. We finally provide potential transfer approaches inspired from our experience, thereby considerably optimizing and simplifying the process.