Large-Area Transfer of 2D TMDCs Assisted by a Water-Soluble Layer for Potential Device Applications

Layer transfer offers enormous potential for the industrial implementation of two-dimensional (2D) material technology platforms. However, the transfer method used must retain the as-grown uniformity and cleanliness in the transferred films for the fabrication of 2D material-based devices. Additionally, the method used must be capable of large-area transfer to maintain wafer-scale fabrication standards. Here, a facile route to transfer centimeter-scale synthesized 2D transition metal dichalcogenides (TMDCs) (3L MoS₂, 1L WS₂) onto various substrates such as sapphire, SiO₂/Si, and flexible substrates (mica, polyimide) has been developed using a water-soluble layer (Na₂S/Na₂SO₄) underneath the as-grown film. The developed transfer process represents a fast, clean, generic, and scalable technique to transfer 2D atomic layers. The key strategy used in this process includes the dissolution of the Na₂S/Na₂SO₄ layer due to the penetration of NaOH solution between the growth substrate and hydrophobic 2D TMDC film. As a proof-of-concept device, a broadband photodetector has been fabricated onto the transferred 3L MoS₂, which shows photoresponse behavior for a wide range of wavelengths ranging from near-infrared (NIR) to UV. The enhancement in photocurrent was found to be 100 times and 10 times the dark current in the UV and visible regions, respectively. The fabricated photodetector shows a higher responsivity of 8.6 mA/W even at a low applied voltage (1.5 V) and low power density (0.6 μW/mm²). The detector enables a high detectivity of 2.9 × 10¹¹ Jones. This work opens up the pathway toward flexible electronics and optoelectronics.