Pick-up and assembling of chemically sensitive van der Waals heterostructures using dry cryogenic exfoliation

TL;DR

This paper introduces a cryogenic exfoliation and transfer technique for assembling high-quality van der Waals heterostructures with pristine interfaces, enabling advanced device fabrication without chemical damage.

Contribution

The authors developed a modified cryogenic micro-manipulation method for assembling vdW heterostructures, preserving interface quality and enabling twisted junctions of complex materials.

Findings

Successfully fabricated twisted heterostructures of BSCCO and NbSe₂.

Transport measurements confirm high interface quality.

Method extends to various vdW materials.

Abstract

Assembling atomic layers of van der Waals materials (vdW) combines the physics of two materials, offering opportunities for novel functional devices. Realization of this has been possible because of advancements in nanofabrication processes which often involve chemical processing of the materials under study; this can be detrimental to device performance. To address this issue, we have developed a modified micro-manipulator setup for cryogenic exfoliation, pick up, and transfer of vdW materials to assemble heterostructures. We use the glass transition of a polymer PDMS to cleave a flake into two, followed by its pick-up and drop to form pristine twisted junctions. To demonstrate the potential of the technique, we fabricated twisted heterostructure of Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (BSCCO), a van der Waals high-temperature cuprate superconductor. We also employed this method to re-exfoliate NbSe$_2$ and make twisted heterostructure. Transport measurements of the fabricated devices indicate the high quality of the artificial twisted interface. In addition, we extend this cryogenic exfoliation method for other vdW materials, offering an effective way of assembling heterostructures and twisted junctions with pristine interfaces.