Damage-free transfer mechanics of 2-dimensional materials: competition between adhesion instability and tensile strain

Chan Kim,Anh Tuan Hoang,Hyeon-Don Kim,Bongkyun Jang,Jong-Hyun Ahn,Min-Ah Yoon,Jae-Hyun Kim,Hak-Joo Lee,Hyun-June Jung,Kwang-Seop Kim

doi:10.1038/s41427-021-00311-1

Abstract

The transfer of two-dimensional (2D) materials is crucial to the realization of 2D material-based devices for practical applications. The thinness of 2D materials renders them prone to mechanical damage during the transfer process and to degradation of their superior electrical and mechanical properties. Herein, the mechanisms involved in the damage of chemical vapor deposition-grown graphene (Gr) and MoS2 are investigated during a roll-based transfer process. We identify two different damage mechanisms, i.e., instability-induced damage and tensile strain-induced damage. The two mechanisms compete, depending on the thickness of the transfer medium, and induce dissimilar damage. By minimizing these two mechanisms, we realize and demonstrate the damage-free transfer of 2D materials. The sheet resistance and mobility of transferred Gr are 235 ± 29 Ω sq–1 and 2250 cm2 V–1 s–1, respectively, with no microscopic cracks or tear-out damage. We observe instability-induced damage to be ubiquitous in monolayer MoS2, thin metals, and thin oxide films. By understanding the instability-induced damage mechanism, a broad range of 2D materials and thin films can be transferred without mechanical damage. Damage-free transfer will contribute to the high-yield fabrication of 2D material-based electronic devices.

Highlights

The transfer of two-dimensional (2D) materials from their growth substrates onto a target substrate is one of the most important step for fabricating 2D heterostructures[1,2] and 2D material-based devices for practical applications3–5. 2D materials such as graphene (Gr)[6,7,8], MoS29,10, and h-BN11–13 can be synthesized with high quality on a large scale but are prone to damage when transferred
To investigate the damage mechanism of 2D materials, the transfer of chemical vapor deposition (CVD)-grown monolayer Gr onto an SiO2/Si wafer was observed in real time using optical microscopy (OM) and a charge-coupled device (CCD) camera system
The compliant layer of the transfer film (TF) was formed by coating a thin PDMS layer onto a polyethylene terephthalate (PET) film

Summary

Introduction

The transfer of two-dimensional (2D) materials from their growth substrates onto a target substrate is one of the most important step for fabricating 2D heterostructures[1,2] and 2D material-based devices for practical applications3–5. 2D materials such as graphene (Gr)[6,7,8], MoS29,10, and h-BN11–13 can be synthesized with high quality on a large scale but are prone to damage when transferred. Transferring large-area 2D materials without any damage is essential for preserving their superior electrical and mechanical properties on a target substrate[14,15]. In 2010, large-area (30-inch) Gr was transferred onto a flexible target substrate using thermal release tape (TRT) as the TF16. The first practical application of large-area Gr transfer was for a touch panel, but TRT residues and cracks in the transferred Gr were problematic. To overcome these drawbacks, a two-layer TF consisting of a hard supporting film and a thin compliant layer in contact with Gr via dispersive adhesion was suggested[17,18]. The TF was further improved by applying a pressuresensitive adhesive film (PSAF) as the compliant layer[19]

Methods

Results

Conclusion