Strongly adhesive dry transfer technique for van der Waals heterostructure

TL;DR

This paper introduces a new dry transfer method using polycaprolactone (PCL) to assemble van der Waals heterostructures with strong adhesion, enabling the fabrication of complex 2D devices with atomically clean interfaces.

Contribution

A novel PCL-based dry transfer technique that enhances adhesion for stacking challenging vdW materials without interface degradation.

Findings

Successfully assembled heterostructures with ZnPS3 and CrPS4.

Demonstrated NbSe2 Josephson junctions with clean interfaces.

Enabled fabrication of complex 2D vdW devices.

Abstract

That one can stack van der Waals materials with atomically sharp interfaces has provided a new material platform of constructing heterostructures. The technical challenge of mechanical stacking is picking up the exfoliated atomically thin materials after mechanical exfoliation without chemical and mechanical degradation. Chemically inert hexagonal boron nitride (hBN) has been widely used for encapsulating and picking up vdW materials. However, due to the relatively weak adhesion of hBN, assembling vdW heterostructures based on hBN has been limited. We report a new dry transfer technique. We used two vdW semiconductors (ZnPS3 and CrPS4) to pick up and encapsulate layers for vdW heterostructures, which otherwise are known to be hard to fabricate. By combining with optimized polycaprolactone (PCL) providing strong adhesion, we demonstrated various vertical heterostructure devices, including quasi-2D superconducting NbSe2 Josephson junctions with atomically clean interface. The versatility of the PCL-based vdW stacking method provides a new route for assembling complex 2D vdW materials without interfacial degradation.