Pick-and-place transfer of arbitrary-metal electrodes for van der Waals device fabrication

TL;DR

This paper introduces a versatile pick-and-place transfer method for arbitrary-metal electrodes onto 2D materials, enabling high-quality interfaces and advancing van der Waals device fabrication.

Contribution

A simple, generalizable transfer technique for pre-fabricated metal electrodes from diamond substrates to 2D materials, avoiding surface treatments and sacrificial layers.

Findings

Successfully transferred eight different metals with varied work functions.

Achieved atomically smooth interfaces with no impurities or disorder.

Demonstrated high-performance transistors with low Schottky barriers.

Abstract

Van der Waals electrode integration is a promising strategy to create near-perfect interfaces between metals and two-dimensional materials, with advantages such as eliminating Fermi-level pinning and reducing contact resistance. However, the lack of a simple, generalizable pick-and-place transfer technology has greatly hampered the wide use of this technique. We demonstrate the pick-and-place transfer of pre-fabricated electrodes from reusable polished hydrogenated diamond substrates without the use of any surface treatments or sacrificial layers. The technique enables transfer of large-scale arbitrary metal electrodes, as demonstrated by successful transfer of eight different elemental metals with work functions ranging from 4.22 to 5.65 eV. The mechanical transfer of metal electrodes from diamond onto van der Waals materials creates atomically smooth interfaces with no interstitial impurities or disorder, as observed with cross-sectional high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy. As a demonstration of its device application, we use the diamond-transfer technique to create metal contacts to monolayer transition metal dichalcogenide semiconductors with high-work-function Pd, low-work-function Ti, and semi metal Bi to create n- and p-type field-effect transistors with low Schottky barrier heights. We also extend this technology to other applications such as ambipolar transistor and optoelectronics, paving the way for new device architectures and high-performance devices.