NaCl-assisted substrate dependent 2D planar nucleated growth of MoS2

Synthesis of large-scale, uniform, easily transferable, and highly crystalline monolayer (1L) molybdenum disulfide (MoS₂) on different substrates is a challenge and could decide its suitability for opto-electronic device applications. Herein, we report a facile NaCl-assisted Chemical Vapor Deposition (CVD) synthesis of high-quality MoS₂ on amorphous, crystalline and layered substrates. Optical microscopy and Raman spectroscopy show that sapphire and SiO₂/Si are suitable substrates for large 1L-MoS₂ flakes growth, while mica is excellent for large-area continuous films. Comparatively lesser full-width-at-half-maximum (FWHM) of predominant A exciton peak in photoluminescence spectra of 1L-MoS₂ on sapphire suggests its high crystalline quality. However, 1L-MoS₂ on other substrates, especially on quartz and bare Si show poor crystalline quality. The study depicts that the NaCl assists in the formation of seeding promoter such as water-soluble layer of Na₂S and/or Na₂SO₄ on the substrate that helps in 2D planar nucleation of MoS₂. The formation of such intermediate seeding layers also helps in layer transfer owing to its easy water solubility. The study could be utilized for large-scale synthesis of 1L-MoS₂ on different substrates for high-performance optoelectronic devices.