Dry Exfoliation of Large-Area 2D Monolayer and Heterostructure Arrays

Abstract

Two-dimensional (2D) semiconductors have attracted considerable attention in recent years. However, to date, there is still no effective approach to produce large-scale monolayers while retaining their intrinsic properties. Here, we report a simple mechanical exfoliation method to produce large-scale and high-quality 2D semiconductors, by designing an atomically flat Au-mesh film as the peeling tape. Using our prefabricated mesh tape, the limited contact region (between the 2D crystal and Au) could provide enough adhesion to mechanically exfoliate uniform 2D monolayers, and the noncontact region (between the mesh holes and monolayers) ensures weak interaction to mechanically release the 2D monolayers on desired substrates. Together, we demonstrate a scalable method to dry exfoliate various 2D monolayer arrays onto different substrates without involving any solutions or contaminations, representing the optimization between material yield, scalability, and quality. Furthermore, detailed optical and electrical characterizations are conducted to confirm their intrinsic quality. With the ability to mechanically exfoliate various 2D arrays and further restacking them, we have demonstrated large-scale van der Waals heterostructure arrays through layer-to-layer assembling. Our study offers a simple and scalable method for dry exfoliating 2D monolayer and heterostructure arrays with intrinsic material quality, which could be crucial to accelerate fundamental investigations as well as practical applications of proof-of-concepts devices.

Can Metals Other than Au be Used for Large Area Exfoliation of MoS2 Monolayers?

“…[11] Flakes produced via this method have already been used in multiple applications including gas sensing, [13] photodetection, [14,15] and heterostructure arrays. [16,17] It has been claimed that the stronger Au/2D TMD interfacial interaction or binding energy (BE) of the top layer overcomes the weaker interlayer van der Waals (VdW) forces between the top layers and subsequent layers in TMD materials, thereby leaving behind largearea ML flakes. [9,12,18] The origin of stronger Au/2D TMDs is due to the well-known affinity of Au towards chalcogen atoms and is well studied in self-assembling monolayers (SAM) formation.…”

2D Heterostructures for Ubiquitous Electronics and Optoelectronics: Principles, Opportunities, and Challenges

“…For 2D heterostructures, dry and polymer-assisted transfers are the most popularly used techniques in mechanically exfoliated 2D materials, liquid-phase-exfoliated 2D materials (Figure b–f and Figure ) (integrated inductively coupled plasma (ICP))/CVD grown-2D materials at micro-and millimeter-size (Figure b-f and Figure ), ,− roll-to-roll-assisted 2D materials, , face-to-face-assisted 2D materials, bubbling transfer-assisted 2D material at millimeter size, mechanically exfoliated 2D material at full wafer size (centimeter), and a quasi-dry transfer of 2D heterostructures through layer-resolved splitting (LRS) (Figure a–c). − Both methods can be used to stack more than two layers of the same or different 2D materials. Polymer residues in both techniques, especially polymer-assisted techniques, dope the 2D material and significantly change the function of a device.…”

Perspectives of 2D Materials for Optoelectronic Integration

“…Large-scale, periodic array of vdW heterojunctions can be produced recently. [231][232][233] Photodetectors using the heterojunction arrays were also demonstrated with reasonable performance. Additionally, as shown in Figure 5f, vdW heterostructures made of multiple kinds of 2D materials can also be explored for photodetection, demonstrating gate-tunable photodiode behavior.…”