Homogeneous and Continuous Liquid Exfoliated Van der Waals MoS2 and WSe2 Thin Films

Emerging 2D materials hold the capacity to revolutionize electronic devices and systems. Yet, as the demand for large-scale applications is rapidly growing, substantial nanofabrication challenges impede 2D materials’ integration in electronic applications. Thin films synthesized via drop casting/Ink-jet printing of 2D-materials inks on silicon substrate typically yields non-uniform distribution of nanoparticles, which is significantly attributed to the "Coffee Ring Effect", which led to incorporating additives and surfactants to 2D-material inks in previous work, altering the pristine nature of the fabricated thin film. In this work, we apply an affordable and facile Liquid Phase Exfoliation (LPE) technique on WSe₂ and MoS₂ powders through suspension in 1:1 Water/Ethanol mixture. We show an induced suppression of the Coffee-ring transport mechanism by controlling evaporation of the solution droplet, which resulted in homogenous and continuous thin films on SiO₂ of an area up to 4.15mm² and 3.14 mm² for 1uL of MoS₂ and WSe₂ solution, respectively. Various parameters such as deposition temperature, droplet volume, droplet solution composition, and particle size and shape on film continuity are explored to induce suppression of coffee ring effect on SiO2 and Si substrates. This work shed some light on fabrication strategies for LPE-2D devices for future electronic applications.