Etching-Free Transfer and Nanoimaging of CVD-Grown MoS₂ Monolayers

Abstract

The transfer of two-dimensional materials from grown substrates onto target substrates is critical for device applications and postgrown analysis. The traditional transfer method for as-grown two-dimensional materials requires a wet chemical etching process that damages the crystals and the substrates. These issues deteriorate the electrical and optical performances of two-dimensional-material-based devices fabricated afterward. Herein, we developed an etching-free method and nanoimaging for transferring and analyzing monolayers of MoS2 onto arbitrary substrates using polyurethane as a sacrifice polymer. The polymer layer and the MoS2 crystals can be peeled off from the substrate by tweezers and transferred to any substrate. We analyzed the transferred samples to a glass coverslip substrate with optical microscopy, atomic force microscopy, tip-enhanced Raman spectroscopy, and tip-enhanced photoluminesce spectroscopy. Also, we transferred monolayers of MoS2 to a transmission electron microscopy grid and acquired scanning electron microscopy together with high-resolution scanning transmission electron microscopy images. The results of nanoimaging indicate that the method preserved the sample’s optical and structural properties and avoid undesirable cracks, wrinkles, and polymer residues. The etching-free transfer method of as-grown two-dimensional materials will improve the quality of transferred samples enhance the devices’ performance.

Edge and 2D states disentanglement and light-driven spin injection in MoS2

“…It is important to note that larger flakes and even films are formed by merging two or more flakes. The previously prepared and magnetically characterized YIG samples were then covered with different amounts and sizes of MoS 2 flakes via an etching-free transfer method [47]. The Raman spectra, Raman map, photoluminescence spectroscopy, atomic force microscopy, and optical microscopy are shown and discussed in the Supplementary information to support the flake quality and transfer method.…”

“…Finally, several samples of YIG with different areas of MoS 2 coverage were prepared. More details about the growth and etch-free transfer method and the characterization of MoS 2 can be found in previous work [45][46][47].…”

Automated mechanical exfoliation technique: a spin pumping study in YIG/TMD heterostructures

“…An alternative solution is to grow over a suitable substrate and then transfer the TMD to the desired substrate. 28 Unfortunately, the transfer process can damage the TMDs and introduce defects and impurities, resulting in a low-quality interface. 29–32…”

“…An alternative solution is to grow over a suitable substrate and then transfer the TMD to the desired substrate. 28 Unfortunately, the transfer process can damage the TMDs and In order to advance the field of nanotechnology and its potential industrial applications, it is crucial to have a simple and efficient method for producing layered materials on a large scale. We report on a simple, affordable, and scalable method to produce transition-metal dichalcogenides (TMDs) thin films with a few layers thick onto Yttrium Iron Garnet (YIG) films based on an automated mechanical abrasion method.…”