High-yield photolithography protocol to pattern metallic electrodes on 2D materials without adhesive metallic layers

Abstract

When using two-dimensional (2D) materials to build electronic devices, adjacent metallic films need to be deposited to form electrodes. However, weak adhesion in high-quality van der Waals interfaces often leads to a low fabrication yield due to materials cracking and even peeling during photolithography. Several researchers use ultra-thin adhesive metallic layers, such as Ti, Cr, or Ni; while this method effectively enhances adhesion, all these metals are oxygen scavengers (in more or less degree) and they significantly alter the charge transport. Here we present a fabrication process for 2D-materials-based electronic devices that leads to high yield without the need of using adhesive metallic layers. Our method consists on using a discontinuous coverage of the 2D material during the photolithography step assisted by a negative photoresist, combined by electron beam evaporation of metal under moderate vacuum (5 × 10⁻⁶ Torr) to produce a truly van der Waals interface and avoid damaging the 2D material. When using this improved method, we systematically achieve defect-free Au/hBN interfaces with good adhesion, which lead to 100 % fabrication yield (340 devices were fabricated correctly). Electrical characterization reveals low leakage currents below 10 pA and minimal device-to-device variability, demonstrating the process’s effectiveness. Our method provides a viable pathway towards the fabrication of 2D material-based electronic devices and circuits with higher performance and reliability.