The comparative defect study on the polymeric transfer of MoS2 monolayers

TL;DR

This study compares wet-transfer and surface-energy-assisted transfer methods for monolayer MoS2, revealing that the latter preserves structural and optical quality better and induces less strain than the conventional wet transfer.

Contribution

It provides a direct comparison of two polymer-based transfer techniques for MoS2, highlighting the advantages of surface-energy-assisted transfer in maintaining material integrity.

Findings

Wet transfer causes KOH contamination and degradation.

Surface-energy-assisted transfer preserves structural integrity.

Surface-energy-assisted transfer results in strain-free monolayers.

Abstract

The defect-free transfer of chemical vapour deposition (CVD) grown monolayer MoS2 is important for both fabrication of 2D devices and fundamental point of view for various studies where substrate effects need to be minimized. Among many transfer techniques, two well-known techniques that use the polymer as carriers are wet-transfer technique and the surface-energy-assisted transfer technique. In this work, we transferred a single CVD grown monolayer MoS2 by these two transfer methods on a similar substrate, and the intervention of strain and defects in the transfer process is probed by Raman and photoluminescence (PL) spectroscopy, respectively. We found that the conventional and commonly used wet transfer technique degraded the monolayer due to KOH contamination. In contrast, monolayers transferred using the surface-energy-assisted transfer method possess structural integrity and optical quality on a par with the as-grown MoS2 layers. As compared to the wet process a strain-free transfer was recorded in the surface-energy-assisted technique using Raman spectroscopic studies.